Spatiotemporal recruitment of human DNA polymerase delta to sites of UV damage.

ABSTRACT: Human DNA polymerase ? (Pol ?) is involved in various DNA damage responses in addition to its central role in DNA replication. The Pol ?4 holoenzyme consists of four subunits, p125, p50, p68 and p12. It has been established that the p12 subunit is rapidly degraded in response to DNA damage by UV leading to the in vivo conversion of Pol ?4 to Pol ?3, a trimeric form lacking the p12 subunit. We provide the first analysis of the time-dependent recruitment of the individual Pol ? subunits to sites of DNA damage produced by UV irradiation through 5 ?m polycarbonate filters by immunofluorescence microscopy and laser scanning cytometry (LSC). Quantitative analysis demonstrates that the recruitments of the three large subunits was near complete by 2 h and did not change significantly up to 4 h after UV exposure. However, the recruitment of p12 was incomplete even at 4 h, with about 70% of the Pol ? lacking the p12 subunit. ChIP analysis of Pol ? after global UV irradiation further demonstrates that only p125, p50 and p68 were present. Thus, Pol ?3 is the predominant form of Pol ? at sites of UV damage as a result of p12 degradation. Using LSC, we have further confirmed that Pol ? was recruited to CPD damage sites in all phases of the cell cycle. Collectively, our results show that Pol ? at the DNA damage site is the Pol ? trimer lacking p12 regardless of the cell cycle phase.

SUBMITTER: Chea J 

PROVIDER: S-EPMC3419061 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature