👤 Bonaventura Clotet

The persistence of latent HIV-1 reservoirs remains a major barrier to achieving a cure for HIV. While latency-reversing agents (LRAs) have been extensively studied, latency-promoting agents (LPAs) offer a complementary strategy to silence viral transcription and prevent immune activation. Here, we propose that modulation of IRF7-driven transcription may represent a novel approach to control HIV-1 latency, by characterizing the role of the Janus kinase 2 inhibitor (JAK2i) pacritinib as a novel latency-promoting agent (LPA). The impact of JAK2i on HIV-1 reactivation, immune activation, and IRF7 expression were evaluated in lymphoid and myeloid HIV-1 latency models, as well as Pacritinib effectively suppressed HIV-1 latency reversal induced by LRAs without triggering immune activation. Mechanistically, pacritinib downregulated IRF7 expression at both transcript and protein levels, correlating with reduced HIV-1 transcription. Overexpression of IRF7 restored LTR transactivation, confirming its central role in HIV-1 transcription and latency. Co-immunoprecipitation assays revealed a direct interaction between IRF7 and the viral transactivator Tat. Furthermore, pacritinib selectively inhibited multiply spliced HIV-1 transcripts, suggesting a blockade at late transcriptional stages. Pacritinib acts as a potent LPA by silencing HIV-1 transcription through IRF7 downregulation, supporting a promising "block and lock" strategy for functional cure approaches. Targeting IRF7 may enable durable suppression of the viral reservoir without immune activation, supporting the development of "block and lock" therapies. Show less

Cell size scales with ploidy in a great range of eukaryotes, but the underlying mechanisms remain unknown. Using various orthogonal single-cell approaches, we show that cell size increases linearly with centromere (CEN) copy number in budding yeast. This effect is due to a G1 delay mediated by increased degradation of Cln3, the most upstream G1 cyclin acting at Start, and specific centromeric signaling proteins, namely Mad3 and Bub3. Mad3 binds both Cln3 and Cdc4, the adaptor component of the Skp1/Cul1/F-box (SCF) complex that targets Cln3 for degradation, these interactions being essential for the CEN-dosage dependent effects on cell size. Our results reveal a pathway that modulates cell size as a function of CEN number, and we speculate that, in cooperation with other CEN-independent mechanisms, it could assist the cell to attain efficient mass/ploidy ratios. Show less

Phosphorus is a pivotal element in all biochemical systems: it serves to store metabolic energy as ATP, it forms the backbone of genetic material such as RNA and DNA, and it separates cells from the environment as phospholipids. In addition to this "big hits", phosphorus has recently been shown to play an important role in other important processes such as cell cycle regulation. In the present review, we briefly summarize the biological processes in which phosphorus is involved in the yeast Saccharomyces cerevisiae before discussing our latest findings on the role of this element in the regulation of DNA replication in this eukaryotic model organism. We describe both the role of phosphorus in the regulation of G1 progression by means of the Cyclin Dependent Kinase (CDK) Pho85 and the stabilization of the cyclin Cln3, as well as the role of other molecule composed of phosphorus-the polyphosphate-in cell cycle progression, dNTP synthesis, and genome stability. Given the eminent role played by phosphorus in life, we outline the future of phosphorus in the context of one of the main challenges in human health: cancer treatment. [Int Microbiol 19(3):133-141 (2016)]. Show less

HIV-infected patients treated with highly active antiretroviral therapy (HAART) may be predisposed to a lipid profile, associated with increased cardiovascular risk, derived from having high triglycerides (TG) and low high-density lipoprotein cholesterol (HDLc) levels. We propose that genetic variability leaves some HIV-infected patients more predisposed to this lipid profile than others. We performed a cross-sectional, observational study including 321 antiretroviral-treated HIV-infected patients classified as normolipidemic (n=173) or presenting with high TG (≥1.7 mmol/liter) and low HDLc [<1.02 (men) or 1.28 mmol/liter (women)] (n=148) to investigate the impact of 13 polymorphisms of 9 genes affecting lipid metabolism (APOA5, APOC3, LPL, CETP, HL, MTP, APOE, LRP5, and VLDLR genes). The polymorphism rs328 in LPL was 40% significantly more frequent in normolipidemics (p=0.018), and in the same group, polymorphisms rs708272 in CETP and rs1800588 in HL were 10% significantly more frequent (p=0.037 for both polymorphisms). Patients who presented a combination of one to six alleles from these polymorphisms had 10% increased HDLc levels [1.13 (0.40) vs. 1.24 (0.23) mmol/liter, p=0.002] and a trend toward lower triglycerides [2.23 (2.34) vs. 1.89 (1.24) mmol/liter] and lower remnant-like particle cholesterol (RLPc) [16.41 (11.42) vs. 12.99 (11.69) mmol/liter]. This effect was dependent on the number of protective alleles and independent of the regimen administered. Polymorphisms in LPL, CETP, and HL protect HIV-infected patients from developing the dyslipidemia derived from high TG and low HDLc levels in a dose-dependent manner. Show less

Several studies have reported associations between lipid parameters and clinical progression of HIV infection. We performed a cross-sectional study including 468 antiretroviral-treated HIV-infected patients to investigate the impact of 13 polymorphisms of 9 genes affecting lipid metabolism and CD4 and CD8-T cell levels. Polymorphisms were identified in genes selected for their role in the development of atherogenic dyslipidemia, defined as triglycerides ⩾1.7mmol/L and high-density lipoprotein cholesterol (HDLc) <1.02 in women or 1.28mmol/L in men. Lipid and lipoprotein parameters were determined in all participants, as well as CD4 and CD8 T-cell counts. ANOVA was performed to compare the mean values of lipid and CD4 and CD8 T-cell count data. A Bonferroni correction for multiple comparisons was applied. 468 patients were included, 148 of them had a diagnosis of atherogenic dyslipidemia. The polymorphism rs3135506 in APOA5 was associated with a 9% increase in triglycerides (p=0.002), 10% and 21% decrease in HDLc (p=0.005), and CD4 T-cell count (p=0.024), respectively. APOA5 rs662799, was associated with a 19% increase in CD8 T-cell count (p=0.002). Carriers of LPL rs328 in the dyslipidemic group presented 11% higher levels of HDLc (p=0.015) and 14% higher levels of CD4 cells (p=0.038). In conclusion, polymorphisms in genes associated to the development of atherogenic dyslipidemia, especially variants in APOA5 gene (rs3135506 and rs662799), can influence the circulating CD4 T-cell levels in chronically HIV-infected patients. These data support previous reports on the effect of lipid metabolism on immunologic parameters in HIV+ individuals on antiretroviral therapy. Show less

HIV-infected patients treated with Highly Active Antiretroviral Therapy (HAART) may be predisposed to hypertriglyceridemia, which gives rise to a highly atherogenic lipid profile known as atherogenic dyslipidemia (AD). We propose that genetic variability leaves some HIV-infected patients more predisposed to AD than others (1, 2). This was a cross-sectional, observational study conducted in 468 antiretroviral-treated HIV-infected patients attending at the outpatient clinic of a tertiary hospital over a 6-month period, who were classified as normolipidemic (n=173) or presenting with AD (triglycerides: 1.7 mmol/L and HDLc < 1.02 [men] or 1.28 mmol/L [women]) (n=148). Polymorphisms were identified in the APOA5, APOC3, LPL, CETP, HL, MTP, APOE, LRP5 and VLDLR genes. Atherogenic dyslipidemia was detected in 31% of patients, most of whom were men (77%). This group was also older and had higher levels of remnant lipoprotein cholesterol (RLPc) than normolipidemic patients. The polymorphisms rs328 in LPL, rs708272 in CETP and rs1800588 in HL were 10-40% significantly more frequent in normolipidemic patients. At least 1 of these polymorphisms was detected in 90% of normolipidemic patients; in AD patients, the percentage decreased to 75% (p=0.003). This effect was dependent on both the allele and the dose of HAART and independent of the regimen administered. The protective combination showed a trend towards higher HDLc (1.13 [0.40] vs 1.24 [0.23] mmol/L), lower triglycerides (2.23 [2.34] vs 1.89 [1.24] mmol/L) and lower RLPc (16.41 [11.42] vs 12.99 [11.69] mmol/L). Polymorphisms in LPL, CETP and HL protect HIV-infected patients from developing AD in a dose-dependent manner (3). Show less

Polymorphisms in some host genes have a significant impact on susceptibility to HIV-1 infection and rate of disease progression (1, 2). The purpose of the current sub-study was to find out the relationship between polymorphisms in genes involved in the lipid metabolism and the CD4/CD8 T-cell counts. Sub-study of a cross-sectional, observational study conducted in 468 patients with HIV infection attended at the outpatient clinic to investigate individual genetic predisposition to atherogenic dyslipidemia (AD). All patients were genetically characterized and all polymorphisms were in Hardy-Weinberg equilibrium. Thirteen polymorphisms were selected from nine genes: APOA5 (rs662799 and rs3135506); APOC3 (rs5128 and rs4520); LPL (rs328 and rs268); CETP (rs708272); HL (rs1800588); MTP (rs1800591); APOE (rs7412 and rs429358); LRP5 (rs7116604); and VLDLR (rs1454626). Lipid and lipoprotein parameters, CD4 and CD8 T-cell counts and plasma HIV-RNA were determinate. The statistical analysis was performed using SPSS statistical software version 19 (SPSS Inc., Chicago, IL, USA). We studied 468 HIV-infected patients (men, 77%), with a mean (SD) age of 45.9 (19.7) years. The mean CD4 T-cell count and nadir CD4 was 547 (459) and 193 (159) cells/µL, respectively; 78.7% of participants were virologically suppressed. Patients carrying rs3135506 in the APOA5 gene presented a 9% increase in circulating TG levels (p=0.002) and 10% decrease in HDLc levels (p=0.005). Such association of APOA5 towards dyslipidemia was accompanied by a 21% decrease of the CD4 T-cell count (p=0.024) and a 19% increase in CD8 T-cell count (p=0.002) in carriers of the rare allele in the APOA5 rs662799 polymorphism adjusted by age and gender. Patients carrying the rare allele in rs5128 (APOC3) had a 16% decrease in circulating CD4 T cells (p=0.029); patients carrying rs1800591 (MTP) had a 29% decrease in CD4 T cells and 14% decrease in CD8 T cells (p=0.018 and p=0.008, respectively); patients carrying the rare allele rs1800588 in HL had a 11% increase in CD4 T cells (p=0.043); and carriers of the rs145626 in the VLDLR gene had 10% decrease in CD4 circulating T cells (p=0.013). Variants in genes involved in the development of AD may also influence the immunological host-virus equilibrium in chronically HIV-infected subjects (2, 3). Show less

G1 cyclins, in association with a cyclin-dependent kinase (CDK), are universal activators of the transcriptional G1-S machinery during entry into the cell cycle. Regulation of cyclin degradation is crucial for coordinating progression through the cell cycle, but the mechanisms that modulate cyclin stability to control cell cycle entry are still unknown. Here, we show that a lack of phosphate downregulates Cln3 cyclin and leads to G1 arrest in Saccharomyces cerevisiae. The stability of Cln3 protein is diminished in strains with low activity of Pho85, a phosphate-sensing CDK. Cln3 is an in vitro substrate of Pho85, and both proteins interact in vivo. More interestingly, cells that carry a CLN3 allele encoding aspartic acid substitutions at the sites of Pho85 phosphorylation maintain high levels of Cln3 independently of Pho85 activity. Moreover, these cells do not properly arrest in G1 in the absence of phosphate and they die prematurely. Finally, the activity of Pho85 is essential for accumulating Cln3 and for reentering the cell cycle after phosphate refeeding. Taken together, our data indicate that Cln3 is a molecular target of the Pho85 kinase that is required to modulate cell cycle entry in response to environmental changes in nutrient availability. Show less

Inactivation of HAL3 in the absence of SIT4 function leads to cell cycle arrest at the G(1)-S transition. To identify genes potentially involved in the control of this phase of the cell cycle, a screening for multicopy suppressors of a conditional sit4 hal3 mutant (strain JC002) has been developed. The screening yielded several genes known to perform key roles in cell cycle events, such as CLN3, BCK2 or SWI4, thus proving its usefulness as a tool for this type of studies. In addition, this approach allowed the identification of additional genes, most of them not previously related to the regulation of G(1)-S transition or even without known function (named here as VHS1-3, for viable in a hal3 sit4 background). Several of these gene products are involved in phospho-dephosphorylation processes, including members of the protein phosphatase 2A and protein phosphatases 2C families, as well as components of the Hal5 protein kinase family. The ability of different genes to suppress sit4 phenotypes (such as temperature sensitivity and growth on non-fermentable carbon sources) or to mimic the functions of Hal3 was evaluated. The possible relationship between the known functions of these suppressor genes and the progress through the G(1)-S transition is discussed. Show less

Yeast cells overexpressing the Ser/Thr protein phosphatase Ppz1 display a slow-growth phenotype. These cells recover slowly from alpha-factor or nutrient depletion-induced G1 arrest, showing a considerable delay in bud emergence as well as in the expression of the G1 cyclins Cln2 and Clb5. Therefore, an excess of the Ppz1 phosphatase interferes with the normal transition from G1 to S phase. The growth defect is rescued by overexpression of the HAL3/SIS2 gene, encoding a negative regulator of Ppz1. High-copy-number expression of HAL3/SIS2 has been reported to improve cell growth and to increase expression of G1 cyclins in sit4 phosphatase mutants. We show here that the described effects of HAL3/SIS2 on sit4 mutants are fully mediated by the Ppz1 phosphatase. The growth defect caused by overexpression of PPZ1 is intensified in strains with low G1 cyclin levels (such as bck2Delta or cln3Delta mutants), whereas mutation of PPZ1 rescues the synthetic lethal phenotype of sit4 cln3 mutants. These results reveal a role for Ppz1 as a regulatory component of the yeast cell cycle, reinforce the notion that Hal3/Sis2 serves as a negative modulator of the biological functions of Ppz1, and indicate that the Sit4 and Ppz1 Ser/Thr phosphatases play opposite roles in control of the G1/S transition. Show less