Poster Presentation The 44th Lorne Conference on Protein Structure and Function 2019

Rad6-18, the master regulator of translesion synthesis (#211)

Brittany M Ripley 1 , Todd Washington 1
  1. University of Iowa, Iowa City, IA, United States

Chemical alterations to DNA bases block the replication fork and can result in fork collapse, single and double stranded breaks, and ultimately cell death. Translesion synthesis (TLS) is a pathway by which a special set of DNA polymerases are recruited to bypass the DNA damage (lesion). These polymerases have active sites that favor specific types of DNA damage, referred to as their cognate lesions. How these polymerases are recruited and the correct polymerase chosen to replicate through its cognate lesion is unclear. Fine-tuned regulation of TLS is critical to prevent high rates of mutagenesis when TLS polymerases replicate past a non-cognate lesion. A key regulatory mechanism of TLS is ubiquitylation of the DNA replication hub protein proliferating cellular nuclear antigen (PCNA) by a ubiquitin ligase complex, Rad6 and Rad18 (Rad6-18). This is thought to recruit TLS polymerases, which include Rev1 and PolĪ·. Our data indicates that Rad6-18 play a more active role in regulating TLS. We found that Rad6-18 interacts directly with two PCNA interacting peptide (PIP) boxes on PolĪ· but can only interact with Rev1 when an autoinhibitory domain is released, indicating temporal recruitment of these polymerases to the DNA damage.These conclusions shed new light on the importance of Rad6-18 to the regulation and function of TLS.