Cells are constantly faced with DNA damage. In order to ensure survival, they require processes that allow for tolerance or repair of these sites, and one such tolerance process is translesion synthesis (TLS). TLS plays a critical role in the SOS response that occurs during DNA damage. In the Escherichia coli SOS response, UmuD is expressed due to damage-induced replication fork stalling which causes a buildup of RecA and ssDNA. Upon expression UmuD forms the homodimer UmuD2, which is a key regulator of the Y family polymerases DinB and UmuC as well as of the replicative DNA polymerase pol III. UmuD seems to function as a switch between these mutagenic repair polymerases and the non-mutagenic DNA replication pathways. The homodimer UmuD2 self-cleaves to form UmuD’2 which combines with UmuC to form DNA polymerase V. Both UmuD2 and UmuD'2 have been shown to interact with the replicative DNA polymerase of E. coli. Whereas interactions between UmuD and the processivity clamp and the DNA polymerase subunit of pol III have been well characterized, far less is known about interactions of UmuD and the processivity clamp loader complex. The clamp loader, consisting of tau, gamma, delta, and delta’ subunits, interact with other proteins within the replisome and coordinate polymerases during DNA replication. Preliminary data suggests that UmuD2 and UmuD'2 interact with clamp loader subunits and may provide additional regulation of DNA replication in response to DNA damage. This study will provide additional insights into the interactions and potential regulation of TLS by UmuD2 and UmuD'2 through these clamp loader subunits, as well as insight into the coordination of the incoming repair polymerases to the stalled fork via the clamp loader assembly.

Mapping the interactions of UmuD and the beta clamp loader in E. coli

2019 Fall National Meeting

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