Periodic Reporting for period 1 - TEI (Development of a model system to study the role of chromatin factors during transgenerational epigenetic inheritance (TEI) in C. elegans)
Berichtszeitraum: 2017-05-01 bis 2019-04-30
One component of this new pathway is an uncharacterised protein with a catalytically dead PARP (poly-ADP polymerase) domain. This finding is crucial since PARP enzymes are important targets in breast and ovarian cancer patients. Further understanding of PARP enzyme regulation and inhibition in C. elegans might have potential therapeutic applications for patients with breast and ovarian cancer. What is more, a potential role for PARP enzymes has been reported in immunological and neurobiological disorders. Our discovery do not just have a potential for a therapeutic application for cancer, but also an additional understanding in neurobiological and immunological disorders.
Interestingly, null mutants f this catalytically dead PARP protein showed synthetic lethality when crossed to a piRNA pathway mutant, hrde-1, at 20C, therefore indicating a parallel pathway. Hence, we started to characterize its role together with catalytically active C. elegans PARP-1 by comparing transcriptome and genome wide binding profiles of wild type and null mutant animals. We found by total RNA sequencing that null mutants desilenced retrotransposons, such as CELE45, to a similar extent, suggesting that these two proteins might function in the same pathway. Additionally, these RNA-seq data sets showed no correlation with those of other known piRNA or nuclear RNAi pathway mutants, demonstrating that they might silence a specific subset of targets. Furthermore, PARP-1 ChIP-seq suggested specific binding on a set of SINE retrotransposons including CELE45 and this enrichment was consistent with PARP-1 ChIP-seq performed in a piRNA pathway mutant.
This new protein with a catalytically dead PARP domain shows domain similarity to the HUSH complex components as well as to the TONSL protein, which interacts with BRCA-1 in humans. Since BRCA-1, together with TONSL, recognize R-loops and single strand DNA breaks as a result of transcription deficiencies and PARP-1 mediates DNA damage repair for single and double strand breaks, we speculate that their specific enrichment on retrotransposons could be transcription-dependent. We are now trying to characterize proteomics analysis in relation to RNA pol II function and DNA damage response on retrotransposons.