Inhibition of DNA synthesis by RB: Effects on G1/S transition and S- phase progression

Erik S. Knudsen, Carolan Buckmaster, Tung Ti Chen, James R. Feramisco, Jean Y J Wang

Research output: Contribution to journalArticlepeer-review

190 Scopus citations


The retinoblastoma tumor suppressor protein, RB, is a negative regulator of cell proliferation. Growth inhibitory activity of RB is attenuated by phosphorylation. Mutation of a combination of phosphorylation sites leads to a constitutively active RB. In Rat-1 cells, the phosphorylation-site-mutated (PSM)-RB, but not wild-type RB, can inhibit S-phase entry. In PSM-RB-arrested G1 cells, normal levels of cyclin E and cyclin E-associated kinase activity were detected, but the expression of cyclin A was inhibited. The ectopic expression of cyclin E restored cyclin A expression and drove the PSM-RB expressing cells into S phase. Interestingly, Rat-1 cells coexpressing cyclin E and PSM-RB could not complete DNA replication. Microinjection of cells that have passed through the G1 restriction point with plasmids expressing PSM- RB also led to the inhibition of DNA synthesis. The S-phase inhibitory activity of PSM-RB could be attenuated by the coinjection of SV40 T-antigen, adenovirus E1A, or a high level of E2F-1 expression plasmids. However, the S- phase inhibitory activity of PSM-RB could not be overcome by the coinjection of cyclin E or cyclin A expression plasmids. These results reveal a novel role for RB in the inhibition of S-phase progression that is distinct from the inhibition of the G1/S transition, and suggest that continued phosphorylation of RB beyond G1/S is required for the completion of DNA replication.

Original languageEnglish (US)
Pages (from-to)2278-2292
Number of pages15
JournalGenes and Development
Issue number15
StatePublished - Aug 1 1998


  • Cyclin A
  • Cyclin E
  • T-antigen
  • p16ink4a
  • p21cip1

ASJC Scopus subject areas

  • Genetics
  • Developmental Biology


Dive into the research topics of 'Inhibition of DNA synthesis by RB: Effects on G1/S transition and S- phase progression'. Together they form a unique fingerprint.

Cite this