Mechanisms of E2F2-mediated transcriptional repression
Laburpena
In this work we wanted to study the mechanism of E2F2-mediated repression. Our
hypothesis is that E2F2 activates the expression of one or more E2F members of the
“repressor” subset of the family through the E2F motifs present in their promoters,
and those repressor E2F(s) would subsequently repress the target promoters.
To address this hypothesis, we focused on E2F7. E2F7 is a repressor that lacks the
Rb binding domain, and associates with DNA through E2F binding sites (de Bruin et
al., 2003). Furthermore, E2F7 itself is also regulated by E2F motifs on its own
promoter, and it has been shown to repress DNA metabolism and replication genes in
late S-phase (de Bruin et al., 2003; Westendorp et al., 2012). E2F7, together with
E2F8 has been found to form heterodimers, being critical on cell proliferation and
development, and both seem to have similar functions (Li et al., 2008).
Preliminary results from Zubiaga’s group have indicated that E2F2 activates E2F7
transcription in U2OS cells, suggesting that E2F2’s repressor function could be mediated by E2F7. For this purpose, we focused on studying E2F7’s role on the
target genes previously known to be repressed by E2F2: Chk1 and Mcm5.
The specific aims for this work were the following:
- Confirm that E2F2 induces E2F7 in HEK-293T cells
- Assess whether E2F7 acts as a transcriptional repressor on E2F sites
- Evaluate the role of E2F7 on E2F2-mediated transcriptional repression of
Chk1 and Mcm5.