Expression of BRCA1, BRCA2, RAD51, and other DSB repair factors is regulated by CRL4WDR70

Modelling DNA damage-repair and beyond

The paper presents a review of mechanistic modelling studies of DNA damage and DNA repair, and consequences to follow in mammalian cell nucleus. We hypothesize DNA deletions are consequences of repair of double strand breaks leading to the modifications of genome that play crucial role in long term development of genetic inheritance and diseases. The aim of the paper is to review formation mechanisms underlying naturally occurring DNA deletions in the human genome and their potential relevance for bridging the gap between induced DNA double strand breaks and deletions in damaged human genome from endogenous and exogenous events. The model of the cell nucleus presented enables simulation of DNA damage at molecular level identifying the spectrum of damage induced in all chromosomal territories and loops. Our mechanistic modelling of DNA repair for double stand breaks (DSB), single strand breaks (SSB) and base damage (BD), shows the complexity of DNA damage is responsible for the longer repair times and the reason for the biphasic feature of mammalian cells repair curves. In the absence of experimentally determined data, the mechanistic model of repair predicts the in vivo rate constants for the proteins involved in the repair of DSB, SSB, and of BD.

Requirement of WDR70 for POLE3-mediated DNA double-strand breaks repair

H2BK120ub1 triggers several prominent downstream histone modification pathways and changes in chromatin structure, therefore involving it into multiple critical cellular processes including DNA transcription and DNA damage repair. Although it has been reported that H2BK120ub1 is mediated by RNF20/40 and CRL4WDR70, less is known about the underlying regulation mechanism for H2BK120ub1 by WDR70. By using a series of biochemical and cell-based studies, we find that WDR70 promotes H2BK120ub1 by interacting with RNF20/40 complex, and deposition of H2BK120ub1 and H3K79me2 in POLE3 loci is highly sensitive to POLE3 transcription. Moreover, we demonstrate that POLE3 interacts CHRAC1 to promote DNA repair by regulation on the expression of homology-directed repair proteins and KU80 recruitment and identify CHRAC1 D121Y mutation in colorectal cancer, which leads to the defect in DNA repair due to attenuated the interaction with POLE3. These findings highlight a previously unknown role for WDR70 in maintenance of genomic stability and imply POLE3 and CHRAC1 as potential therapeutic targets in cancer.