👤 Shengguo Zhao

Tumor cells are metabolically reprogrammed to fuel cell proliferation. Most transformed cells take up high levels of glucose and produce ATP through aerobic glycolysis. In cells exhibiting aerobic glycolysis, a significant fraction of glucose carbon is also directed into de novo lipogenesis and nucleotide biosynthesis. The glucose-responsive transcription factor carbohydrate responsive element binding protein (ChREBP) was previously shown to be important for redirecting glucose metabolism in support of lipogenesis in nonproliferating hepatocytes. However, whether it plays a more generalized role in reprogramming metabolism during cell proliferation has not been examined. Here, we demonstrated that the expression of ChREBP can be induced in response to mitogenic stimulation and that the induction of ChREBP is required for efficient cell proliferation. Suppression of ChREBP resulted in diminished aerobic glycolysis, de novo lipogenesis, and nucleotide biosynthesis, but stimulated mitochondrial respiration, suggesting a metabolic switch from aerobic glycolysis to oxidative phosphorylation. Cells in which ChREBP was suppressed by RNAi exhibited p53 activation and cell cycle arrest. In vivo, suppression of ChREBP led to a p53-dependent reduction in tumor growth. These results demonstrate that ChREBP plays a key role both in redirecting glucose metabolism to anabolic pathways and suppressing p53 activity. Show less

The mechanism by which niacin increases plasma levels of high-density lipoprotein cholesterol (HDL-C) is not clearly understood yet. Adipocytes contain the largest pool of free cholesterol in the body and might play a significant role in cholesterol metabolism. Despite preferential accumulation in adipose tissue, it is not clear whether the actions of niacin on cholesterol efflux from adipocytes contribute to its HDL-raising effect. Fully differentiated 3T3-L1 adipocytes were incubated in the medium containing various concentrations of niacin (0-1.0 mmol/l) for 24 h. Reverse transcription polymerase chain reaction was used to evaluate peroxisome proliferator-activated receptor-gamma (PPARgamma), LXRalpha and ABCA1 mRNA expression in adipocytes. Cholesterol efflux rate was determined by measuring the release of radioactivity from (3)H-cholesterolprelabeled cells into medium containing apolipoprotein A-I (ApoA-I). Niacin dose-dependently stimulated PPARgamma, LXRalpha and ABCA1 mRNA expression and promoted ApoA-I-induced cholesterol efflux in adipocytes. Treatment of PPARgamma-selective antagonist GW9662 significantly abolished the niacin-induced increase in LXRalpha and ABCA1 mRNA expression and cholesterol efflux to ApoA-I. Niacin may promote cholesterol efflux from adipocytes to ApoA-I via activation of the PPARgamma-LXRalpha-ABCA1 pathway. To some extent, this effect might help to explain the possible mechanism by which niacin increases plasma HDL-C levels. Show less

Hyperlipidemia is one of the most important risk factors for atherosclerosis. This can be amplified by a localized inflammatory response mediated by macrophages. Macrophages are capable of taking up excess cholesterol, and it is well known that delivery of cholesterol to the mitochondria by steroidogenic acute regulatory (StAR) protein is the rate-limiting step for cholesterol degradation in the liver. It has also been shown that overexpression of StAR in hepatocytes dramatically increases the amount of regulatory oxysterols in the nucleus, which play an important role in the maintenance of intracellular lipid homeostasis. The goal of the present study was to determine whether StAR plays a similar role in macrophages. We have found that overexpression of StAR in human THP-1 monocyte-derived macrophages decreases intracellular lipid levels, activates liver X receptor alpha (LXRalpha) and proliferation peroxysome activator receptor gamma (PPARgamma), and increases ABCG1 and CYP27A1 expression. Furthermore, it reduces the secretion of inflammatory factors, and prevents apoptosis. These results suggest that StAR delivers cholesterol to mitochondria where regulatory oxysterols are generated. Regulatory oxysterols can in turn activate nuclear receptors, which increase expression of cholesterol efflux transporters, and decrease secretion of inflammatory factors. These effects can prevent macrophage apoptosis. These results imply a potential role of StAR in the prevention of atherosclerosis. Show less

Histone deacetylase inhibitor (HDACi) has been shown to demethylate the mammalian genome, which further strengthens the concept that DNA methylation and histone modifications interact in regulation of gene expression. Here, we report that an HDAC inhibitor, depsipeptide, exhibited significant demethylating activity on the promoters of several genes, including p16, SALL3, and GATA4 in human lung cancer cell lines H719 and H23, colon cancer cell line HT-29, and pancreatic cancer cell line PANC1. Although expression of DNA methyltransferase 1 (DNMT1) was not affected by depsipeptide, a decrease in binding of DNMT1 to the promoter of these genes played a dominant role in depsipeptide-induced demethylation and reactivation. Depsipeptide also suppressed expression of histone methyltransferases G9A and SUV39H1, which in turn resulted in a decrease of di- and trimethylated H3K9 around these genes' promoter. Furthermore, both loading of heterochromatin-associated protein 1 (HP1alpha and HP1beta) to methylated H3K9 and binding of DNMT1 to these genes' promoter were significantly reduced in depsipeptide-treated cells. Similar DNA demethylation was induced by another HDAC inhibitor, apicidin, but not by trichostatin A. Our data describe a novel mechanism of HDACi-mediated DNA demethylation via suppression of histone methyltransferases and reduced recruitment of HP1 and DNMT1 to the genes' promoter. Show less

In selecting a method to produce a recombinant protein, a researcher is faced with a bewildering array of choices as to where to start. To facilitate decision-making, we describe a consensus 'what to try first' strategy based on our collective analysis of the expression and purification of over 10,000 different proteins. This review presents methods that could be applied at the outset of any project, a prioritized list of alternate strategies and a list of pitfalls that trip many new investigators. Show less

LINGO-1 has been critically implicated in the central regulation of CNS axon regeneration and oligodendrocyte maturation. We have recently demonstrated that pretreatment with LINGO-1 antagonist (LINGO-1-Fc) inhibited low potassium-induced cerebellar granular neurons (CGNs) apoptosis. In the present study, we examined the neuroprotective mechanism of LINGO-1-Fc by Western blot and in situ GST pull-down assay. CGN cultures were preincubated in medium with LINGO-1-Fc or control protein at the concentration of 10 mug/ml for 2 h and then switched to low potassium medium in the presence of corresponding proteins. Cultures were harvested at indicated time intervals for successive analysis. Several apoptosis-associated signaling factors, GSK-3beta, ERK1/2, and Rho GTPases, were observed to be activated in response to potassium deprivation and the activation/dephosphorylation of GSK-3beta was suppressed by LINGO-1-Fc pretreatment compared with control group. Besides, the endogenous LINGO-1 expression level of CGN cultures was augmented by low potassium stimuli and restrained by LINGO-1 antagonist treatment. Although the protein level of p75(NTR) and Nogo-A were down-regulated in different patterns during apoptosis, neither of them was affected by LINGO-1-Fc application. Taken together, these results suggest a new mechanism of LINGO-1 antagonist regulated neuronal survival involving protein synthesis of LINGO-1 and inactivation of GSK-3 pathway. Show less

The PIK3C3 gene has been implicated as a candidate gene for schizophrenia by functional evidence and genetic association studies. A series of previous studies have found susceptibility SNPs in promoter region. To further verify its susceptibility to schizophrenia in the Chinese population and the function of the polymorphisms, we performed a case control study in 556 unrelated schizophrenia patients and 563 normal controls as well as an in vitro functional analysis. In our association analysis of-432C-/T, we discovered obvious differences in allele frequency between patients and controls (P=0.017). A T/C haplotype constructed by -432C-/T and -86insC, which are tightly linked with each other (r(2)=1) can significantly weaken promoter's transcriptional activity by 20% (p=0.002 by t-test). Though we cannot exclude the possibility that susceptibility of -432C-/T is caused by its linkage disequilibrium with other causal variants, our results do support PIK3C3 play a significant role in the etiology of schizophrenia. Show less

To investigate the changes of several protein markers in a metastatic colorectal carcinoma model by serum proteomic analysis. The pEGFP-N1 plasmid with enhanced expression of green fluorescence protein (EGFP) was transfected into human colon carcinoma cell line SW480 to obtain a stable SW480-EGFP cell line, the SW480-EGFP cells were then injected subcutaneously into nude mice. The harvested tumor cells were implanted orthotopically into the colon of the nude mice. Real-time tumor growth and metastasis formation were visualized by whole-body fluorescent imaging system. Serum samples at different metastatic stages were collected and differential proteomic profiles were investigated by two-dimensional gel electrophoresis (2DE) and matrix-assisted laser absorption/ionization time of flight mass spectrometry (MALDI-TOF MS). The SW480- EGFP cells enabled to express EGFP stably. The rates of subcutaneous and orthotropic tumor formation were 100%. The metastasis rates to local lymph nodes, liver and lung were 100%, 40% and 30%, respectively. Furthermore, 5 differentially expressed proteins were analyzed by serum proteome technologies, including haptoglobin alpha chain, apolipoprotein E, apolipoprotein A-IV, Ig kappa chain V region chain L and transferrin. Visualized metastatic model of colorectal carcinoma was successfully established. Several differentially expressed serum proteins collected at different stages after the occurrence of metastasis were identified. These differentially expressed proteins may be candidate serum biomarkers for diagnosis and therapeutic evaluation of colorectal carcinoma metastasis. Show less

To investigate the association between the apolipoprotein A5(APOA5) -1131T/C polymorphism and premature coronary heart disease in northern Chinese Han population. Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and polyacrylamide gel electrophoresis (PAGE), we analyzed the genotype and allele distribution in 140 patients with premature coronary heart disease diagnosed by coronary angiography and 156 healthy controls. The levels of serum lipid profiles were also studied by biochemical methods. The allele frequency of APOA5-1131T/C polymorphism in the premature coronary heart disease group was significantly higher (43.2% vs. 33.0%, P=0.011) than that in the control group. Compared with TT homozygotes, CC homozygotes exhibited a 2.809-fold (95% CI 1.331-5.927) increased risk of developing premature coronary heart disease. Logistic regression analysis found that this correlation was independent of sex, age, body mass index (BMI), smoking history as well as serum total cholesterol(TC), high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C) levels; In premature coronary heart disease group, the triglyceride(TG) level in CC homozygotes was significantly higher than those in TC heterozygotes or TT homozygotes. The APOA5-1131T/C polymorphism has influence on serum TG level, and the APOA5-1131C allele is associated with the development of premature coronary heart disease in northern Chinese Han population. Show less

Apolipoprotein A5 (ApoA5) is present in human serum at a very low concentration. We developed a new method to determine ApoA5 concentration in human serum, and to investigate the correlation between serum ApoA5 and the lipid profiles in healthy subjects, and to analyze whether the correlation was affected by gender. All the subjects (total 92, male 50, female 42) were healthy subjects without any medication. Lipids were measured enzymatically. An ELISA performed by a couple of monoclonal antibodies was used to measure serum ApoA5. The average ApoA5 concentration was 182.7+/-104.7 ng/ml ranging from 5.4 to 455.6 ng/ml. Serum ApoA5 concentration was negatively correlated with TG in female (r=-0.496, P=0.001). In all subjects, ApoA5 concentration was positively correlated to HDL-C (r=0.453, P<0.001). This correlation was more predominant in female (r=0.617, P<0.001) than in male (r=0.289, P=0.042). ApoA5 concentration was negatively correlated to body mass index (BMI) with more significance in female than in male (r=-0.345, P=0.001 for all; r=-0.456, P=0.002 for female; r=-0.198, P=0.167 for male). The serum concentration of ApoA5 was very low. The concentration of ApoA5 was negatively correlated with TG and BMI, but positively correlated with HDL-C. The correlations were affected by gender. Show less

Nogo-A has been considered as one of the most important myelin-associated axonal regeneration inhibitors in the central nervous system. Recent studies have demonstrated various additional physiological roles of Nogo family members. To understand the possible effect of Nogo-A on the differentiation of oligodendrocytes, antibodies against distinct extracellular domains of Nogo-A were applied in cell cultures. Oligodendrocyte precursor cells from P2 rat cortex were grown in the presence of monoclonal antibody against the N-terminal inhibitory domain of Nogo-A or the C-terminal 66 amino acid loop of Nogo-A for 3 days, and the antibody treatment resulted in stunted process extension and inhibited differentiation of oligodendrocytes. Concomitant with morphology changes, Rho GTPases activity was greatly increased upon the antibody treatment and the expression level of LINGO-1, which was recently shown to be a negative regulator for the oligodendrocyte maturation, was upregulated in the process of antibody treatment. These results indicate that endogenous Nogo-A expressed in oligodendrocyte may act though Rho GTPase and LINGO-1 to influence the morphological differentiation of oligodendrocytes and will help us to understand the physiology role of Nogo-A in oligodendrocyte biology. Show less

Ubiquitination and the degradation of the large subunit of RNA polymerase II, Rpb1, is not only involved in DNA damage-induced arrest but also in other transcription-obstructing events. However, the ubiquitin ligases responsible for DNA damage-independent processes in mammalian cells remain to be identified. Here, we identified Wwp2, a mouse HECT domain ubiquitin E3 ligase, as a novel ubiquitin ligase of Rpb1. We found that Wwp2 specifically interacted with mouse Rpb1 and targeted it for ubiquitination both in vitro and in vivo. Interestingly, the interaction with and ubiquitination of Rpb1 was dependent neither on its phosphorylation state nor on DNA damage. However, the enzymatic activity of Wwp2 was absolutely required for its ubiquitin modification of Rpb1. Furthermore, our study indicates that the interaction between Wwp2 and Rpb1 was mediated through WW domain of Wwp2 and C-terminal domain of Rpb1, respectively. Strikingly, downregulation of Wwp2 expression compromised Rpb1 ubiquitination and elevated its intracellular steady-state protein level significantly. Importantly, we identified six lysine residues in the C-terminal domain of Rpb1 as ubiquitin acceptor sites mediated by Wwp2. These results indicate that Wwp2 plays an important role in regulating expression of Rpb1 in normal physiological conditions. Show less

To explore the possible mechanism of apoptosis induced by photodynamic therapy (PDT) in human pancreatic cancer cells Capan-1 with 2-butylamino-2-demethoxy-hypocrellin B (BAHB) as photosensitizer. The localization of BAHB in Capan-1 cells was studied, apoptosis was determined by DNA gel electrophoresis after PDT. The mitochondria membrane potential (DYm) and cytochrome C release were observed by laser scan confocal microscopy and Western blotting. The low concentration photosensitizer was mainly localized in mitochondria and also in lysosomes when the concentration is high. DNA ladder analysis showed characteristic of apoptosis. The mitochondria membrane potential (DYm) showed a loss of 30% around, after 6 hours by PDT under laser scan confocal microscopy, which is caused by a sudden increase in the permeability of mitochondria membrane accompanied with apoptosis. In Western blotting, cytochrome C release was observed from the mitochondria into the cytoplasm during BAHB-induced apoptosis. The research suggests that BAHB-induced apoptosis is related to photosensitization of mitochondria. Show less

Although oligonucleotide chips, cDNA microarrays, differential display reverse transcription-PCR, and other approaches have been used to screen implantation-related molecules, the mechanism by which embryo implantation occurs is still unknown. The aim of this study was to profile the differential gene expression between interimplantation site and implantation site in mouse uterus on day 5 of pregnancy by serial analysis of gene expression (SAGE). In our two SAGE libraries of 11-bp tags, the total numbers of tags sequenced were 48,121 for the interimplantation site and 50,227 for the implantation site. There were 1,039 tags specifically expressed at interimplantation site, and 1,252 tags specifically expressed at the implantation site. Based on the p value, there were 195 tags significantly up-regulated at the interimplantation site and 261 tags significantly up-regulated at the implantation site, of which 100 genes were single matched at the interimplantation site and 127 genes were single matched at the implantation site, respectively. By reverse transcription-PCR, the tag ratio between the implantation site and interimplantation site was verified on 14 significantly changed genes. Using in situ hybridization, 1810014L12Rik, Psmb5, Cd63, Npm1, Fads3, and Tagln2 were shown to be highly expressed at the implantation site compared with the interimplantation site. Compared with the interimplantation site, Ddx39 was strongly expressed in the subluminal stromal cells at the implantation site on day 5 of pregnancy. Ddx39 expression at the implantation site was specifically induced by active blastocysts. Additionally, Ddx39 expression was significantly up-regulated by estrogen in the ovariectomized mice. In our SAGE data, many implantation-related genes were identified in mouse uterus. Our data could be a valuable source for future study on embryo implantation. Show less

A polysaccharide from the water extract of cultured Cordyceps militaris was isolated through ethanol precipitation, deproteination and gel-filtration chromatography. Their molecular weight was determined using gel-filtration chromatography. The structure of polysaccharide CPS-1 was elucidated by sugar analysis, Smith degradation, IR and 13C-NMR spectroscopy. CPS-1 was shown to possess a significant antiinflammatory activity and suppressed the humoral immunity in mice but had no significant effects on the cellular immunity and the non-specific immunity. Show less

To identify novel regulators of Galpha(o), the most abundant G-protein in brain, we used yeast two-hybrid screening with constitutively active Galpha(o) as bait and identified a new regulator of G-protein signaling (RGS) protein, RGS17 (RGSZ2), as a novel human member of the RZ (or A) subfamily of RGS proteins. RGS17 contains an amino-terminal cysteine-rich motif and a carboxyl-terminal RGS domain with highest homology to hRGSZ1- and hRGS-Galpha-interacting protein. RGS17 RNA was strongly expressed as multiple species in cerebellum and other brain regions. The interactions between hRGS17 and active forms of Galpha(i1-3), Galpha(o), Galpha(z), or Galpha(q) but not Galpha(s) were detected by yeast two-hybrid assay, in vitro pull-down assay, and co-immunoprecipitation studies. Recombinant RGS17 acted as a GTPase-activating protein (GAP) on free Galpha(i2) and Galpha(o) under pre-steady-state conditions, and on M2-muscarinic receptor-activated Galpha(i1), Galpha(i2), Galpha(i3), Galpha(z), and Galpha(o) in steady-state GTPase assays in vitro. Unlike RGSZ1, which is highly selective for G(z), RGS17 exhibited limited selectivity for G(o) among G(i)/G(o) proteins. All RZ family members reduced dopamine-D2/Galpha(i)-mediated inhibition of cAMP formation and abolished thyrotropin-releasing hormone receptor/Galpha(q)-mediated calcium mobilization. RGS17 is a new RZ member that preferentially inhibits receptor signaling via G(i/o), G(z), and G(q) over G(s) to enhance cAMP-dependent signaling and inhibit calcium signaling. Differences observed between in vitro GAP assays and whole-cell signaling suggest additional determinants of the G-protein specificity of RGS GAP effects that could include receptors and effectors. Show less

The POU transcription factor Oct-4 is a master regulator affecting the fate of pluripotent embryonic stem cells. However, the precise mechanisms by which the activation and expression of Oct-4 are regulated still remain to be elucidated. We describe here a novel murine ubiquitin ligase, Wwp2, that specifically interacts with Oct-4 and promotes its ubiquitination both in vivo and in vitro. Remarkably, the expression of a catalytically inactive point mutant of Wwp2 abolishes Oct-4 ubiquitination. Moreover, Wwp2 promotes Oct-4 degradation in the presence of overexpressed ubiquitin. The degradation is blocked by treatment with proteasome inhibitor. Fusion of a single ubiquitin to Oct-4 inactivates its transcriptional activity in a heterologous Oct-4-driven reporter system. Furthermore, overexpression of Wwp2 in embryonic stem cells significantly reduces the Oct-4-transcriptional activities. Collectively, we demonstrate for the first time that Oct-4 can be post-translationally modified by ubiquitination and that this modification dramatically suppresses its transcriptional activity. These results reveal that the functional status of Oct-4, in addition to its expression level, dictates its transcriptional activity, and the results open up a new avenue to understand how Oct-4 defines the fate of embryonic stem cells. Show less

Modification of synaptic NMDA receptor (NMDAR) expression influences NMDAR-mediated synaptic function and associated persistent pain. NMDARs directly bind to a family of membrane-associated guanylate kinases (MAGUKs) that regulate surface and synaptic NMDAR trafficking in the CNS. We report here that postsynaptic density-93 protein (PSD-93), a postsynaptic neuronal MAGUK, is expressed abundantly in spinal dorsal horn and forebrain, where it colocalizes and interacts with NMDAR subunits NR2A and NR2B. Targeted disruption of the PSD-93 gene reduces not only surface NR2A and NR2B expression but also NMDAR-mediated excitatory postsynaptic currents and potentials, without affecting surface AMPA receptor expression or its synaptic function, in the regions mentioned above. Furthermore, mice lacking PSD-93 exhibit blunted NMDAR-dependent persistent pain induced by peripheral nerve injury or injection of Complete Freund's Adjuvant, although they display intact nociceptive responsiveness to acute pain. PSD-93 appears to be important for NMDAR synaptic targeting and function and to be a potential biochemical target for the treatment of persistent pain. Show less

ANBL-6, a myeloma cell line, proliferates in response to interleukin 6 (IL-6) stimulation, coculture with bone marrow stromal cells, and when harboring a constitutively active mutant N-ras gene. Eighteen samples, including 4 IL-6-treated, 3 mutant N-ras-transfected, 3 normal stroma-stimulated, 2 multiple myeloma (MM) stroma-stimulated, and 6 untreated controls were profiled using microarrays interrogating 12 626 genes. Global hierarchical clustering analysis distinguished at least 6 unique expression signatures. Notably, the different stimuli altered distinct functional gene programs. Class comparison analysis (P =.001) revealed 138 genes (54% involved in cell cycle) that distinguished IL-6-stimulated versus nontreated samples. Eighty-seven genes distinguished stroma-stimulated versus IL-6-treated samples (22% encoded for extracellular matrix [ECM] proteins). A total of 130 genes distinguished N-ras transfectants versus IL-6-treated samples (26% involved in metabolism). A total of 157 genes, 20% of these involved in signaling, distinguished N-ras from stroma-interacting samples. All 3 stimuli shared 347 genes, mostly of metabolic function. Genes that distinguished MM1 from MM4 clinical groups were induced at least by one treatment. Notably, only 3 genes (ETV5, DUSP6, and KIAA0735) are uniquely induced in mutant ras-containing cells. We have demonstrated gene expression patterns in myeloma cells that distinguish an intrinsic genetic transformation event and patterns derived from both soluble factors and cell contacts in the bone marrow microenvironment. Show less

A flow controlling system for pulsed inhaled nitric oxide has been developed and tested, and here its features and initial animal experiments and clinical applications are described. The physical characteristic test indicates that the practical released dose of NO gas is very close to the theoretical flow of NO gas at variant pressures. Animal experiments demonstrate that inhaled NO gas concentration is lower than the concentration of theoretical inhalation, but the variance is not remarkable (p>0.05). When sixteen cases with CHD and PH were chosen to inhale NO gas (15 ppm, 15 min) PAP and PVR of all cases were reduced after inhalation of NO gas from 617 +/-51.3 dyn x s x cm(-5), 54.4+/-13.1 mmHg to 417+/-36.9 dym x s x cm(-5), 33.8+/-12.3 mmHg (PVR, p<0.01; PAP, p<0.01) respectively. When gas inhalation was stopped, these values returned to their base lines after a short period of time. All these show that the pulsed inhaled NO flow controlling instrument in accordance with the requirements of the designing, can be widely used in clinical diagnoses and treatments and will be a new tool offered for the treatments of the patients with PH. Show less

To evaluate the relationship between plasma apoA-IV levels and coronary atherosclerosis and to explore its relation to other risk factors. Using ELISA techniques, plasma apoA-IV levels were quantified in 181 patients who underwent coronary angiography (CAG). Patients were divided according to their coronary status into a coronary heart disease (CHD) group (stenotic lesion on CAG, n = 118) and a control group (normal CAG, n = 63). The severity of atherosclerosis was assessed by stenosis scoring of the different lesions. Other parameters, including apoA-I, apoB, Lp(a), HDL-C, LDL-C, TG, and TC, were measured as well. Univariate, logistic regression analyses were used to define the relationship between coronary atherosclerosis and plasma apoA-IV levels. When compared with the control group, plasma apoA-IV levels were found to be lower in the CHD group. There was a weak negative correlation between plasma apoA-IV levels and the severity of coronary atherosclerosis. ApoA-IV was found to be a relatively independent risk factor for CHD. We also found a positive correlation between apoA-IV and triglyceride levels. ApoA-IV may be important in the prediction of CHD and coronary atherosclerosis severity. It may also play an important role in the metabolism of triglycerides. Show less

The p38 group of kinases belongs to the mitogen-activated protein (MAP) kinase superfamily with structural and functional characteristics distinguishable from those of the ERK, JNK (SAPK), and BMK (ERK5) kinases. Although there is a high degree of similarity among members of the p38 group in terms of structure and activation, each member appears to have a unique function. Here we show that activation of p38gamma (also known as ERK6 or SAPK3), but not the other p38 isoforms, is required for gamma-irradiation-induced G(2) arrest. Activation of the MKK6-p38gamma cascade is sufficient to induce G(2) arrest in cells, and expression of dominant negative alleles of MKK6 or p38gamma allows cells to escape the DNA damage-induce G(2) delay. Activation of p38gamma is dependent on ATM and leads to activation of Cds1 (also known as Chk2). These data suggest a model in which activation of ATM by gamma irradiation leads to the activation of MKK6, p38gamma, and Cds1 and that activation of both MKK6 and p38gamma is essential for the proper regulation of the G(2) checkpoint in mammalian cells. Show less

Invins(10;11)(p12;q23q12) is one of the rare but recurring chromosome rearrangements seen in acute monoblastic leukemia. We cloned the proximal 10p breakpoint from one patient and showed that the MLL gene at 11q23 was fused to the 3' portion of AF10 at 10p12. In addition, we cloned the telomeric 10p junction and we found that the 5' portion of AF10 was juxtaposed to a previously unidentified gene at 11q12, which we call HEAB (a human homolog to a hypothetical Caenorhabditis elegans ATP/GTP-binding protein). These results indicate that the AF10 gene is split into a 5' AF10 and a 3' AF10 portion by the 11q23q12 chromosome segment and that both breakpoint junctions result in fusion transcripts of 5' AF10/HEAB and MLL/3' AF10. Only the MLL/3' AF10 fusion mRNA results in an in-frame fusion. Northern blot analysis of HEAB expression shows that a 2.0-kb major transcript is expressed ubiquitously in human tissues and is especially abundant in testis and skeletal muscle, whereas a 3.2-kb minor transcript is noted with the highest level of expression in thymus and peripheral blood leukocytes. The HEAB gene encodes a 425-amino acid protein that is rich in valine and leucine. HEAB protein shows high homology in its entire amino acid sequence to a putative C elegans protein and contains an adenosine triphosphate (ATP)/guanosine triphosphate (GTP)-binding motif that has homology to the ATP-binding transporter superfamily or to GTP-binding proteins. Our results could explain the high frequency of complex insertion and other rearrangement events that involve 10p12 and 11q12 and 11q23. The finding that different portions of a single gene are involved in fusions with two independent genes in the same leukemic cell is unique in the analysis of chromosome translocations. Show less