The retinoblastoma protein is phosphorylated during specific phases of the cell cycle

Cell. 1989 Sep 22;58(6):1097-105. doi: 10.1016/0092-8674(89)90508-4.


p105-RB is the product of the retinoblastoma tumor suppressor gene. It is a nuclear phosphoprotein hypothesized to act as an inhibitor of cellular proliferation, yet surprisingly it is present in actively dividing cells. To look for changes in p105-RB that may regulate its activity during the cell cycle, we generated synchronized cell populations and followed their progression through the cell cycle. p105-RB is synthesized throughout the cycle, but is phosphorylated in a phase-specific manner. In the G0 and G1 phases of the cell cycle, an unphosphorylated species of the protein is the only detectable form, whereas in the S and G2/M phases, multiple phosphorylated species of p105-RB are detected.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Cycle*
  • DNA Replication
  • Eye Neoplasms / genetics*
  • Flow Cytometry
  • HeLa Cells / cytology
  • HeLa Cells / metabolism
  • Humans
  • Immunoblotting
  • Interphase
  • Mitosis
  • Phosphoproteins / biosynthesis
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Retinoblastoma / genetics*
  • Retinoblastoma Protein
  • Suppression, Genetic*


  • Phosphoproteins
  • Retinoblastoma Protein