Regulation of the Drosophila transcription factor E2f1 (2012)

Undergraduates: Tatyana Zhuravleva, none Jean Davidson none

Faculty Advisor: Robert Duronio
Department: Biology

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The E2F transcription factors are key regulators of the metazoan cell cycle, and as such, must be tightly controlled themselves. In Drosophila, activator E2f1 is repressed by Rb in G1 of the cell cycle, and targeted for destruction by the E3 ubiquitin ligase CRL4(Cdt2) via interacting with PCNA in S-phase. Because PCNA is also present on DNA during DNA damage repair, we asked whether E2f1 is destroyed in a PCNA-dependent manner during DNA repair, or if E2f1 is stable during DNA repair, as mammalian E2F1 is. To test whether E2f1 is destroyed in a PCNA-dependent manner during DNA repair, we used a Drosophila cell line called S2 cells in an in-vitro assay. To recruit PCNA to replication forks, DNA was damaged with UV-irradiation, and E2f1 levels were measured by Western blotting during the repair process. To identify the domain responsible for the stability of E2f1 during DNA repair, transfected S2 cells expressing variously truncated exogenous E2f1s will be subjected to the UV test and the exogenous E2f1s will be monitored for behavior that is different from endogenous E2f1. Current data suggest that E2f1 is not destroyed during DNA damage repair. The E2f1 domain responsible for protection of E2f1 from PCNA-dependent proteolysis during DNA repair is currently being investigated. The apparently facultative PCNA-dependent proteolysis of E2f1 implies that the regulation of E2f1 is multifaceted and that activator E2Fs of metazoans may have a conserved function in DNA damage repair.