Splicing controls the ubiquitin response during DNA double-strand break repair.

Although evidence that splicing regulates DNA repair is accumulating, the underlying mechanism(s) remain unclear. Here, we report that short-term inhibition of pre-mRNA splicing by spliceosomal inhibitors impairs cellular repair of DNA double-strand breaks. Indeed, interference with splicing as little as 1 h prior to irradiation reduced ubiquitylation of damaged chromatin and impaired recruitment of the repair factors WRAP53ß, RNF168, 53BP1, BRCA1 and RAD51 to sites of DNA damage. Consequently, splicing-deficient cells exhibited significant numbers of residual γH2AX foci, as would be expected if DNA repair is defective. Furthermore, we show that this is due to downregulation of the E3 ubiquitin ligase RNF8 and that re-introduction of this protein into splicing-deficient cells restores ubiquitylation at sites of DNA damage, accumulation of downstream factors and subsequent repair. Moreover, downregulation of RNF8 explains the defective repair associated with knockdown of various splicing factors in recent genome-wide siRNA screens and, significantly, overexpression of RNF8 counteracts this defect. These discoveries reveal a mechanism that may not only explain how splicing regulates repair of double-strand breaks, but also may underlie various diseases caused by deregulation of splicing factors, including cancer.

Downregulation of the cancer susceptibility protein WRAP53ß in epithelial ovarian cancer leads to defective DNA repair and poor clinical outcome.

Alterations in the scaffold protein WRAP53ß have previously been linked to carcinogenesis and, in particular, associated with an increased risk for epithelial ovarian cancer. Here, we investigated the pathogenic impact and prognostic significance of WRAP53ß in connection with epithelial ovarian cancer and examined the underlying mechanisms. We find that reduced expression of WRAP53ß in ovarian tumors correlated with attenuated DNA damage response and poor patient survival. Furthermore, in ovarian cancer cell lines, WRAP53ß was rapidly recruited to DNA double-strand breaks, where it orchestrated the recruitment of repair factors involved in homologous recombination and non-homologous end joining, including RNF168, 53BP1, BRCA1 and RAD51. Mechanistically, WRAP53ß accomplishes this by facilitating the necessary ubiquitinylation at DNA breaks. Finally, we demonstrate that loss of WRAP53ß significantly impairs the repair of DNA double-strand breaks, resulting in their accumulation. Our findings establish WRAP53ß as a regulator of homologous recombination and non-homologous end joining repair in ovarian cancer cells, suggesting that loss of this protein contributes to the development and/or progression of ovarian tumors. Moreover, our current observations identify the nuclear levels of WRAP53ß as a promising biomarker for the survival of patients with ovarian cancer.

p53-directed translational control can shape and expand the universe of p53 target genes.

The increasing number of genome-wide transcriptome analyses focusing on p53-induced cellular responses in many cellular contexts keeps adding to the already numerous p53-regulated transcriptional networks. To investigate post-transcriptional controls as an additional dimension of p53-directed gene expression responses, we performed a translatome analysis through polysomal profiling on MCF7 cells upon 16 hours of doxorubicin or nutlin-3a treatment. The comparison between the transcriptome and the translatome revealed a considerable level of uncoupling, characterized by genes whose transcription variations did not correlate with translation variations. Interestingly, uncoupled genes were associated with apoptosis, DNA and RNA metabolism and cell cycle functions, suggesting that post-transcriptional control can modulate classical p53-regulated responses. Furthermore, even for well-established p53 targets that were differentially expressed both at the transcriptional and translational levels, quantitative differences between the transcriptome, subpolysomal and polysomal RNAs were evident. As we searched mechanisms underlying gene expression uncoupling, we identified the p53-dependent modulation of six RNA-binding proteins, where hnRNPD (AUF1) and CPEB4 are direct p53 transcriptional targets, whereas SRSF1, DDX17, YBX1 and TARDBP are indirect targets (genes modulated preferentially in the subpolysomal or polysomal mRNA level) modulated at the translational level in a p53-dependent manner. In particular, YBX1 translation appeared to be reduced by p53 via two different mechanisms, one related to mTOR inhibition and the other to miR-34a expression. Overall, we established p53 as a master regulator of translational control and identified new p53-regulated genes affecting translation that can contribute to p53-dependent cellular responses.

[Cytomegalovirus-induced protein-losing gastropathy: a case report]. / Un raro caso di gastroenteropatia ipertrofica protido-disperdente da CMV.

Protein-losing gastropathy is an uncommon disease of uncertain etiology, known also as Menetrier's disease. In medical literature only 50 pediatric cases have been described. These childhood forms, in contrast to classic adult Menetrier's disease, have a typical benign and transient course, and require only supportive therapy. The role of Cytomegalovirus (CMV) in the pathogenesis has been demonstrated by gastric biopsy in one third of the cases. Also other infectious, allergic and immunological factors have been hypothesized. We describe a case of hypertrophic gastropathy with important protein-loss, admitted to our Pediatric Department for evaluation because of vomit, weight loss, abdominal pain and hypoalbuminemia. Gastric mucosal biopsy revealed a morphological evidence of CMV infection.