Ithaca College

 Mark Hedglin ´05 of Penn State, PA will present Regulation of PCNA monoubiquitination, a post-translational modification critical to DNA Damage Tolerance

Tuesday, September 18th 12:10 pm in CNS 333
Pizza and Beverages Provided

DNA damage tolerance (DDT) permits bypass of DNA damages encountered during S-phase and may be carried out by translesion DNA synthesis (TLS). In humans, efficient TLS requires the selective monoubiquitination of PCNA sliding clamps encircling damaged DNA. This posttranslational modification (PTM) is catalyzed by Rad6/Rad18. Currently, it is unclear how this critical PTM is regulated throughout the cell cycle.  In particular, it is unknown how the selectivity of this critical PTM is achieved and maintained throughout the cell cycle.  Furthermore, it is unknown how this PTM is carried out in the context of DDT where a plethora of PCNA-binding proteins compete for access to sliding clamps. To address these and other questions, we developed a fluorescence-based assay to quantitatively monitor the covalent attachment of ubiquitin to target proteins under various conditions. Results from extensive studies reveal that the human single-strand DNA binding protein, RPA, promotes the selective monoubiquitination of PCNA sliding clamps encircling DNA throughout the cell cycle. Interestingly, DNA polymerases delta and eta, both of which are imperative for DDT after exposure to ultraviolet radiation, inhibit monoubiquitination of PCNA.  Altogether, these results unveil novel insights into the spatio-temporal regulation of human DDT.    

Individuals with disabilities requiring accommodations should contact Paula Larsen at plarsen@ithaca.edu or (607) 274-3238. We ask that requests for accommodations be made as soon as possible.