Ovarian carcinoma has still a poor prognosis. CRISPR/Cas9 loss-of-function screen revealed a relationship between the PSMC6 proteasome subunit expression and survival of cisplatin-sensitive and -resis Show more
Ovarian carcinoma has still a poor prognosis. CRISPR/Cas9 loss-of-function screen revealed a relationship between the PSMC6 proteasome subunit expression and survival of cisplatin-sensitive and -resistant ovarian carcinoma cells. Increased levels of PSMC6 were evidenced in multiple ovarian carcinoma cell lines versus normal cells. An association between PSMC6 levels and tumour stages as well as with a reduced progression-free survival was found. Since a PSMC6 interactome analysis evidenced limited knowledge on PSMC6 biology, mechanistic studies were carried out. PSMC6 knockdown indicated reduced cell growth and clonogenicity in cisplatin-sensitive IGROV-1 and -resistant IGROV-1/Pt1 cells, with a higher impact in resistant cells. This behaviour was accompanied by the accumulation of ubiquitinated proteins and down-regulation of ERK1/2 phosphorylation mediated by increased DUSP6. PSMC6 silencing increased sensitivity to cisplatin in IGROV-1/Pt1 cells as shown by clonogenic assay and 3D spheroids. Since PSMC6 knockdown did not change sensitivity to 20S and 19S proteasome inhibitors, we suggest a new mode of proteasome targeting by interference with a proteasome ATPase. Overall, a link between PSMC6 and ovarian carcinoma aggressiveness is envisioned, highlighting PSMC6 as a potential diagnostic and therapeutic target. Show less
Post-transcriptional regulatory processes may change transcript levels and affect cell-to-cell variability or noise. We study small-RNA downregulation to elucidate its effects on noise in the iron hom Show more
Post-transcriptional regulatory processes may change transcript levels and affect cell-to-cell variability or noise. We study small-RNA downregulation to elucidate its effects on noise in the iron homeostasis network of Escherichia coli In this network, the small-RNA RyhB undergoes stoichiometric degradation with the transcripts of target genes in response to iron stress. Using single-molecule fluorescence in situ hybridization, we measured transcript numbers of the RyhB-regulated genes sodB and fumA in individual cells as a function of iron deprivation. We observed a monotonic increase of noise with iron stress but no evidence of theoretically predicted, enhanced stoichiometric fluctuations in transcript numbers, nor of bistable behavior in transcript distributions. Direct detection of RyhB in individual cells shows that its noise is much smaller than that of these two targets, when RyhB production is significant. A generalized two-state model of bursty transcription that neglects RyhB fluctuations describes quantitatively the dependence of noise and transcript distributions on iron deprivation, enabling extraction of in vivo RyhB-mediated transcript degradation rates. The transcripts' threshold-linear behavior indicates that the effective in vivo interaction strength between RyhB and its two target transcripts is comparable. Strikingly, the bacterial cell response exhibits Fur-dependent, switch-like activation instead of a graded response to iron deprivation. Show less