WRN participates in translesion synthesis pathway through interaction with NBS1

Abstract

Werner syndrome (WS), caused by mutation of the WRN gene, is an autosomal recessive disorder associated with premature aging and predisposition to cancer. WRN belongs to the RecQ DNA helicase family, members of which play a role in maintaining genome stability. Here, we demonstrate that WRN rapidly forms discrete nuclear foci in an NBS1-dependent manner following DNA damage. NBS1 physically interacts with WRN through its FHA domain, which interaction is important for the phosphorylation of WRN. WRN subsequently forms DNA damage-dependent foci during the S phase, but not in the G1 phase. WS cells exhibit an increase in spontaneous focus formation of pol η and Rad18, which are important for translesion synthesis (TLS). WRN also interacts with PCNA in the absence of DNA damage, but DNA damage induces the dissociation of PCNA from WRN, leading to the ubiquitination of PCNA, which is essential for TLS. This dissociation correlates with ATM/NBS1-dependent degradation of WRN. Moreover, WS cells show constitutive ubiquitination of PCNA and interaction between PCNA and Rad18 E3 ligase in the absence of DNA damage. Taken together, these results indicate that WRN participates in the TLS pathway to prevent genomic instability in an ATM/NBS1-dependent manner.

Increased oxidative stress in AOA3 cells disturbs ATM-dependent DNA damage responses

“…HeLa, U2OS, hTERT-immortalized human fibroblast (48BR), hTERT-immortalized AOA3 patient-derived fibroblast (PSFhTERT), SV40-trasformed normal fibroblast (MRC5SV), and SV40-transformed AOA3 patient-derived fibroblast (PSF-SV) [10,26] cells were cultured in Dulbecco's modified Eagle medium (Sigma) supplemented with 10% fetal bovine serum (FBS; Invitrogen) and antibiotics. Normal human (GM2184, C2ABR, and C3ABR; [10,14]), AT patient-derived (CSA [27]), and AOA3 patient lymphoblastoid cells (ATL2ABR [10]) were cultured in Roswell Park Memorial Institute medium (Sigma) supplemented with 10% FBS and antibiotics.…”

“…Western blot analysis was carried out as described previously [26]. Target proteins were detected with the primary antibodies mentioned above and horseradish peroxidase (HRP)-conjugated anti-rabbit IgG or anti-mouse IgG antibodies (GE Healthcare).…”

RECQL1 and WRN Proteins Are Potential Therapeutic Targets in Head and Neck Squamous Cell Carcinoma

“…Notably, only WRN helicase possesses an exonuclease activity (10). RECQL1 and WRN proteins are members of the RecQ helicase family and play an important role in maintenance of genomic stability (5,(11)(12)(13)(14). RECQL1 functions as a Holliday junction-resolving enzyme and is involved in a mismatch-repair pathway; and the defect is possibly linked to tumorigenesis of colorectal cancers (15).…”

Human DNA Polymerase η and Its Regulatory Mechanisms

“…WRN interacts with and stimulates the polymerase activities of TLS polymerases Polh, Poli and Polk (54). WRN also regulates TLS as the WRN-NBS1 interaction is important for RAD18-mediated PCNA ubiquitination (55,56).…”