ANLN directly interacts with PCNA to regulate UV induced translesion synthesis

Anillin (ANLN) is a cytoskeletal binding protein involved in mitosis. ANLN is located in the nucleus during interphase and in the cytoplasmic contractile rings during mitosis. Our previous studies found that ANLN is abnormally overexpressed in esophageal squamous cell carcinoma (ESCC), promoting cell division by regulating contractile ring localization. However, the exact function of ANLN in the nucleus remains unclear. Here, we found that the expression of ANLN in the nucleus is associated with poor prognosis in ESCC patients, rather than in the cytoplasm. Protein mass spectrometry and bioinformatics analysis revealed that ANLN is related to DNA synthesis, and proliferating cell nuclear antigen (PCNA) is found to be a potential interacting protein of ANLN. PCNA directly interacts with the PIP box domain of ANLN and co-localizes in the nucleus. ANLN promotes DNA replication and S phase progression in a PCNA dependent manner and independent with the cytoskeletal function of ANLN. Importantly, ANLN is involved in transletion synthesis (TLS), a type of DNA synthesis under stress, by promoting PCNA monoubiquitination at K164 residue. Mechanistically, ANLN binds and recruits the E3 ligase RAD18 to promote PCNA monoubiquitination and DNA polymerase eta loading under UV radiation conditions. Consistently, depletion of ANLN leads to increased genomic instability and increased sensitivity to UV radiation. The findings of the study showed that ANLN in the nucleus as a protein scaffold is involved in UV induced DNA synthesis pathway, providing new insights into the function and mechanism of ANLN in cancer cells.