title: DNA polymerase eta is targeted by Mdm2 for polyubiquitination and proteasomal degradation in response to ultraviolet irradiation.
abstract: DNA polymerase eta (PolH), the product of the xeroderma pigmentosum variant (XPV) gene and a Y-family DNA polymerase, plays a pivotal role in translesion DNA synthesis. Loss of PolH leads to early onset of malignant skin cancer in XPV patients and increases UV-induced carcinogenesis. Thus, the pathways by which PolH expression and activity are controlled may be explored as a strategy to prevent UV-induced cancer. In this study, we found that Mdm2, a RING finger E3 ligase, promotes PolH degradation. Specifically, we showed that knockdown of Mdm2 increases PolH expression in both p53-proficient and -deficient cells. In addition, we showed that UV-induced PolH degradation is attenuated by Mdm2 knockdown. In contrast, ectopically expression of Mdm2 decreases PolH expression, which can be abrogated by the proteasome inhibitor MG132. Moreover, we showed that Mdm2 physically associates with PolH and promotes PolH polyubiquitination in vivo and in vitro. Finally, we showed that knockdown of Mdm2 increases the formation of PolH replication foci and decreases the sensitivity of cells to UV-induced lesions in a PolH-dependent manner. Taken together, we uncovered that Mdm2 serves as an E3 ligase for PolH polyubiquitination and proteasomal degradation in cells under the basal condition and in response to UV irradiation.
authors: Comparative Oncology Laboratory, University of California, Davis, CA 95616, USA.
authors: Yong-Sam
authors: YS
authors: Jung
authors: Yingjuan
authors: Y
authors: Qian
authors: Xinbin
authors: X
authors: Chen
mesh_terms: D016923:Cell Death / Q000528:radiation effects; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D025821:Polyubiquitin / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding / Q000528:radiation effects; D059748:Proteolysis / Q000528:radiation effects*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects*; D000099270:Y-Family DNA Polymerases
chemical_list: D004259:DNA-Directed DNA Polymerase; D025821:Polyubiquitin; D046988:Proteasome Endopeptidase Complex; D051736:Proto-Oncogene Proteins c-mdm2; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases