Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Jamie Lopez


DPC, E3 ligase, Mms21, Siz1, SUMO/Smt3, Wss1


Cells are constantly under threat from both exogenous and endogenous sources of DNA damage. Eukaryotic organisms, however, possess conserved mechanisms that accurately and faithfully respond to DNA damage. The inability to effectively remove DNA lesions can lead to an accumulation of mutations which can compromise cellular viability. The DNA damage response is conserved from bacteria to eukaryotic organisms and have been well characterized, however, how covalently crosslinked proteins are removed from DNA remains enigmatic This thesis provides genetic and biochemical evidence implicating Wss1, a yeast metalloprotease in genome maintenance. We have identified SUMOylation to be an important signal that mediates the removal of as DNA-protein crosslinks. DNA protein crosslinks (DPC) are lethal lesions which are covalently linked to DNA. These lesions can impeding essential DNA transactions including chromosome duplication, chromatin remodeling and gene transcription. We characterized Siz1 and Mms21 E3 SUMO ligases to be important for modifying DPCs. To further expand the role of Mms21 in DPC repair we probed the impact of structural maintenance of chromosome (SMC) mutants in repairing DPCs. This thesis shows that Wss1 is involved in cleaving histones in order to prevent their accumulation during hydroxyurea induced replication stress. In vitro cleavage assays with purified proteins indicate that Wss1’s histone H3 cleavage activity is dependent on its protease activity alone and not its SUMO binding nor p97 domains, unlike in Wss1- mediated removal of DNA-protein crosslinks. Together, we provide molecular evidence suggesting that Wss1 is an important mediator in genome maintenance.

Library of Congress Subject Headings

DNA-protein interactions.
Proteins -- Crosslinking.
DNA repair.



Number of Pages



South Dakota State University



Rights Statement

In Copyright