Authored: Gopinathrao, G, 2004-06-16 19:22:00 E2F1 binds to E2F binding sites on the genome activating the synthesis of the target proteins. For annotation purposes, the reactions regulated by E2F1 are grouped under this pathway and information about the target genes alone are displayed for annotation purposes. <br>Cellular targets for activation by E2F1 include thymidylate synthetase, Rir2, Dihydrofolate reductase, Cdc2, Cyclin A1, Cdc6 (DeGregori et al., 1995), Cdt1 (Yoshida and Inoue, 2004), CDC45 (Arata et al., 2000), CDC6 (Yan et al., 1998; Ohtani et al., 1998), Cyclin E (Ohtani et al., 1996), Emi1 (Hsu et al., 2002), and Orc1 (Ohtani et al., 1997). The activation of TK2 (Dnk1) and Cdc25A by E2F1 have been inferred from similar events in Drosophila (Duronio and O'Farrell, 1994;Reis and Edgar, 2004). <br>Rir2 protein is involved in dNTP level regulation and activation of this enzyme results in higher levels of dNTPs in anticipation of S-phase. E2F activation of Rir2 has been shown also in Drosophila by Duronio and O'Farrell (1994). E2F1 activation of CDC45 is shown in mouse cells by using human E2F1 construct (Arata et al., 2000). Cyclin E is also transcriptionally regulated by E2F1. Cyclin E protein plays important role in the transition of G1 in S-phase by associating with Cdk2 (Ohtani et al., 1996). E2F activation of PCNA has been demonstrated in Drosophila (DeGregori et al., 1995) and in some human cells by using recombinant adenovirus constructs. E2F activation of Polymerase A (Pol A) has been demonstrated in some human cells. It has also been demonstrated in Drosophila by Ohtani and Nevins (1994). It has been observed in Drosophila that E2F1 regulated expression of Orc1 stimulates ORC1-6 complex formation and binding to the origin of replication (Asano and Wharton, 1999). Orc1-6 recruit Cdc6 and Cdt1 that are required to recruit the MCM2-7 replication helicases. E2F1 regulation incorporates a feedback mechanism where in Geminin can inhibit MCM2-7 recruitment of ORC1-6 complex by interacting with Cdc6/Cdt1. The activation of Cdc25A and TK2 (Dnk1) by E2F1 has been inferred from similar events in Drosophila (Duronio RJ, O'Farrell 1994; Reis and Edgar, 2004). E2F1 activates string (Cdc25) that in turn activates Cyclin B/Cdk1. A similar phenomenon has been observed in mouse NIH 3T3 cells and in Rat1 cells. Reviewed: Bosco, G, 2004-06-16 19:24:21

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