Updated project metadata. DNA polymerase  (pol) is a Y-family translesion synthesis polymerase that plays a key role in the cellular tolerance toward UV irradiation-induced DNA damage. Here, we identified, for the first time, the phosphorylation of serine 687 (S687), which islocated in the highly conserved nuclear localization signal (NLS) region of human pol and is mediated by cyclin-dependent kinase 2 (CDK2). We also showed that this phosphorylation is stimulated in human cells upon UV light exposure and results in diminished interaction of pol with proliferating cell nuclear antigen (PCNA). Furthermore, we demonstrated that the phosphorylation of S687 in polconfers cellular protection fromUV irradiation and increases the efficiency in replication across a site-specifically incorporated cyclobutane pyrimidine dimer in human cells. Based on these results, we proposed a mechanistic model where S687 phosphorylation functions in the reverse polymerase switching step of translesion synthesis: The phosphorylation brings negative charges to the NLS of pol, which facilitates its departure from PCNA, thereby resetting the replication fork for highly accurate and processive DNA replication. Thus, our study, together with previous findings, supported that the post-translational modifications of NLS of pol played a dual role in polymerase switching, where K682 deubiquitination promotes the recruitment of pol to PCNA immediately prior to lesion bypass and S687 phosphorylation stimulates its departure from the replication fork immediately after lesion bypass.