Geminin is targeted for repression by the retinoblastoma tumor suppressor pathway through intragenic E2F sites

Michael Markey, Hasan Siddiqui, Erik S. Knudsen

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


The geminin protein is a critical regulator of DNA replication. It functions to control replication fidelity by blocking the assembly of prereplication complexes in the S and G2 phases of the cell cycle. Geminin protein levels, which are low in G0/G1 and increase at the G1/S transition, are controlled through coordinate transcriptional and proteolytic regulation. Here we show that geminin is regulated transcriptionally by the retinoblastoma tumor suppressor (RB)/E2F pathway. Initially, we observed that the activation of RB led to the repression of geminin transcription. Conversely, Rb-null mouse embryonic fibroblasts have enhanced the expression of geminin relative to wild type mouse embryonic fibroblasts. Similarly, an acute loss of Rb in mouse adult fibroblasts deregulated geminin RNA and protein levels. To delineate the responsible regulatory motifs, luciferase reporter constructs containing fragments of the geminin promoter were generated. An analysis of the critical regulatory cis-acting elements in the geminin promoter indicated that intragenic E2F sites down-stream of the first exon were responsible for RB-mediated repression of geminin. The direct analysis of the endogenous geminin promoter revealed that these intragenic E2F sites are occupied by E2F proteins, and the mutation of these sites eliminates responsiveness to RB. Together, these data link the expression of geminin to the RB/E2F pathway and represent the first promoter analysis of this important regulator of DNA replication.

Original languageEnglish (US)
Pages (from-to)29255-29262
Number of pages8
JournalJournal of Biological Chemistry
Issue number28
StatePublished - Jul 9 2004

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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