Regulation of the ATR signalling pathway by Adenovirus

Ad5 and Ad12 inhibit ATR-dependent Chk1 phosphorylation. Ad5 E4orf3 promotes the relocalization of the MRN complex in order to inhibit Chk1 activation during infection, whereas Ad12 E4orf3 is unable to inactivate MRN by this method. Here we show that Ad12 inhibits Chk1 phosphorylation by targeting TopBP1, Timeless and Tipin for degradation. We have determined that Ad12 E4orf6 associates with the cellular Cul2-containing ubiquitin ligase to promote TopBP1 degradation. We have shown that Ad5 and Ad12 differentially activate Cullin-containing ubiquitin ligase complexes during infection. Furthermore, we have also determined that Ad12 E4orf3 promotes the degradation of Timeless and Tipin in an Ad12E1B-55k/E4orf6-independent, and Cul2-dependent fashion, during infection. Previous research from our laboratory identified WDR62 as possible E1B-55K interacting protein. The second aim of this study was to expand our current knowledge of this protein and determine its role during infection. Here we show that E1B-55K interacts with WDR62 in vivo and colocalizes with it at centrosomes. We also provide evidence to show that WDR62 functions in the cellular DNA damage response. Indeed, cells depleted of WDR62 by RNA interference resulted in a UV-sensitive phenotype, defects in ATR activation and G2/M checkpoint control, as well as displaying supernumerary centrosome during mitosis.