The N-terminal domain of the Drosophila retinoblastoma protein Rbf1 interacts with ORC and associates with chromatin in an E2F independent manner

PLoS One. 2008 Jul 30;3(7):e2831. doi: 10.1371/journal.pone.0002831.


Background: The retinoblastoma (Rb) tumor suppressor protein can function as a DNA replication inhibitor as well as a transcription factor. Regulation of DNA replication may occur through interaction of Rb with the origin recognition complex (ORC).

Principal findings: We characterized the interaction of Drosophila Rb, Rbf1, with ORC. Using expression of proteins in Drosophila S2 cells, we found that an N-terminal Rbf1 fragment (amino acids 1-345) is sufficient for Rbf1 association with ORC but does not bind to dE2F1. We also found that the C-terminal half of Rbf1 (amino acids 345-845) interacts with ORC. We observed that the amino-terminal domain of Rbf1 localizes to chromatin in vivo and associates with chromosomal regions implicated in replication initiation, including colocalization with Orc2 and acetylated histone H4.

Conclusions/significance: Our results suggest that Rbf1 can associate with ORC and chromatin through domains independent of the E2F binding site. We infer that Rbf1 may play a role in regulating replication directly through its association with ORC and/or chromatin factors other than E2F. Our data suggest an important role for retinoblastoma family proteins in cell proliferation and tumor suppression through interaction with the replication initiation machinery.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • Cell Nucleus / metabolism
  • Cell Proliferation
  • Chromatin / chemistry
  • Chromatin / metabolism
  • Drosophila / metabolism*
  • Drosophila Proteins / metabolism*
  • E2F Transcription Factors / chemistry*
  • Fluorescence Resonance Energy Transfer
  • Histones / chemistry
  • Models, Biological
  • Origin Recognition Complex
  • Photobleaching
  • Protein Binding
  • Protein Structure, Tertiary
  • Retinoblastoma Protein
  • Transcription Factors / metabolism*


  • Chromatin
  • Drosophila Proteins
  • E2F Transcription Factors
  • Histones
  • Origin Recognition Complex
  • Rbf protein, Drosophila
  • Retinoblastoma Protein
  • Transcription Factors