DNA damage tolerance permits bypass of DNA lesions encountered during S-phase and may be carried out by translesion DNA synthesis (TLS). Human TLS requires selective monoubiquitination of proliferating cell nuclear antigen (PCNA) sliding clamps encircling damaged DNA.  This posttranslational modification (PTM) is catalyzed by Rad6/Rad18. Recent studies revealed that replication protein A (RPA), the major ssDNA-binding protein, is involved in the regulation of PCNA monoubiquitination and interacts directly with Rad18 on chromatin and in the nucleoplasm. However, it is unclear how RPA regulates this critical PTM and what functional role(s) these interactions serve. In this study published in The Journal of Biological Chemistry, we developed an in vitro fluorescence assay to quantitatively monitor PCNA monoubiquitination under in vivo scenarios. Results from extensive experiments revealed that RPA regulates Rad6/Rad18 activity in a ssDNA-dependent manner.
Check out the full article here: http://www.jbc.org/content/early/2019/01/30/jbc.RA118.005297.abstract
Check out the highlights of this article in the “News and Research Spotlights” from the PSU department of chemistry here:https://science.psu.edu/news/hedglin-group-makes-strides-cancer-research