POLD4
Developmental stage
Expression is cell cycle-dependent, with highest levels in G2/M phase and a drastic drop in S phase (PubMed:22801543, PubMed:23913683). This trough may be mediated by DCX(DTL) E3 ubiquitin ligase complex (also called CRL4(CDT2))-mediated proteasomal degradation (PubMed:23913683).
Function
As a component of the tetrameric DNA polymerase delta complex (Pol-delta4), plays a role in high fidelity genome replication and repair. Within this complex, increases the rate of DNA synthesis and decreases fidelity by regulating POLD1 polymerase and proofreading 3' to 5' exonuclease activity (PubMed:16510448, PubMed:19074196, PubMed:20334433). Pol-delta4 participates in Okazaki fragment processing, through both the short flap pathway, as well as a nick translation system (PubMed:24035200). Under conditions of DNA replication stress, required for the repair of broken replication forks through break-induced replication (BIR), a mechanism that may induce segmental genomic duplications of up to 200 kb (PubMed:24310611). Involved in Pol-delta4 translesion synthesis (TLS) of templates carrying O6-methylguanine or abasic sites (PubMed:19074196). Its degradation in response to DNA damage is required for the inhibition of fork progression and cell survival (PubMed:24022480).
Post-translational modifications
Ubiquitinated; undergoes 'Lys-48'-linked ubiquitination in response to UV irradiation, leading to proteasomal degradation (PubMed:16934752, PubMed:17317665, PubMed:23233665, PubMed:23913683). This modification is partly mediated by RNF8 and by the DCX(DTL) E3 ubiquitin ligase complex (also called CRL4(CDT2)) (PubMed:23233665, PubMed:24022480). Efficient degradation requires the presence of PCNA and is required for the inhibition of fork progression after DNA damage (PubMed:24022480).
Sequence Similarities
Belongs to the DNA polymerase delta subunit 4 family.
Cellular localization
- Nucleus
- Partially recruited to DNA damage sites within 2 hours following UV irradiation, before degradation.
Alternative names
POLDS, POLD4, DNA polymerase delta subunit 4, DNA polymerase delta subunit p12