Understanding the Role of RNF4 in Genome Maintenance
Ring finger protein 4 (RNF4) is a small ubiquitin-like modifier (SUMO)- targeted E3 ubiquitin ligase that recognizes SUMOylated proteins and attaches ubiquitin to them. This protein takes part in various cell cycle regulated processes, including DNA replication and functions under challenging conditions, such as stalling of the replication fork. However, the exact role that RNF4 has in genome maintenance is still unclear. Here, we show that RNF4 plays an important role in DNA replication, by relieving replication fork stress and enabling proper elongation through the cell cycle. We found that RNF4 knockout retinal pigmented epithelial 1 (RPE1) cell lines exhibit higher anaphase abnormalities during mitosis, compared to RNF4-proficient cell lines. The anaphase abnormalities were more common in RNF4 knockout cell lines that were treated with the proteasome inhibitor bortezomib. Furthermore, the RNF4 mutant cell lines have increased levels of p53 binding protein 1 (53BP1) nuclear bodies, which suggests that they under-replicate DNA. In addition, we are investigating whether these cells have utilized MiDAS as the last attempt to repair under-replicated DNA before the cells divide.