Functions of a subunit of DNA polymerase δ, POLD3, revealed by depletion of WRNIP1
Akari Yoshimura1, Takuya Abe1, Kouji Hirota2
1Division of Biochemistry, Faculty of Pharmaceutical Sciences, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, 981-8558, Japan.
Abstract:
Werner helicase-interacting protein 1 (WRNIP1) binds to Polδ and promotes its activity in vitro; however, the functional relationship between WRNIP1 and Polδ in the DNA damage tolerance process remains unclear. In this study, we performed genetic analyses of WRNIP1 and Polδ in the chicken DT40 cell line by generating WRNIP1AID/POLD3- (POLD3 is the p66 subunit of Polδ) conditional knockout cells using the auxin degron system, where the WRNIP1and POLD3 genes are knocked out, and degradation-inducible WRNIP1AID is expressed. Upon auxin treatment, the ultraviolet (UV) sensitivity of WRNIP1AID/POLD3- cells was suppressed and compared to that of the POLD3- cells or WRNIP1AID/POLD3- cells without auxin. Additionally, a decrease in cyclobutane pyrimidine dimers was seen in WRNIP1AID/POLD3- cells following WRNIP1AID depletion at 24 h after UV irradiation. The mutation induction rate after UV irradiation did not change in auxin-treated WRNIP1AID/POLD3- cells compared to that of single mutant cells or WRNIP1AID/POLD3- cells cultured without auxin. UV-induced sister chromatid exchange (SCE), a process mediated by homologous recombination, was higher in POLD3-cells than in wild-type cells, whereas SCE in WRNIP1AID/POLD3- cells was moderately increased by depletion of WRNIP1AID. We have identified a genetic interaction between WRNIP1 and POLD3. We will discuss the potential molecular mechanisms underlying this interaction.
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