p130, p107, and pRb Are Differentially Regulated in Proliferating Cells and during Cell Cycle Arrest by α-Interferon

• Published in: The Journal of biological chemistry Vol. 273; no. 37; p. 23659
• Main Authors: Nicholas S. B. Thomas, Arnold R. Pizzey, Sanjay Tiwari, Catherine D. Williams, Jiewu Yang
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 11.09.1998
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.37.23659

We have determined how the phosphorylation of the retinoblastoma family (pRb, p107, and p130) is governed in individual cell cycle phases of Daudi B-cells during cell cycle exit triggered by α-interferon (α-IFN). α-IFN causes dephosphorylation of pRb and loss of p130 phosphorylated Form 3. However, the change in p130 phosphorylation in response to α-IFN occurs before dephosphorylation of pRb is complete because loss of p130 Form 3 occurs throughout the cell cycle prior to complete arrest in G 1 , whereas pRb is dephosphorylated only in G 1 . In contrast, p107 is dephosphorylated and is then depleted from cells as they exit the cell cycle. p130, predominantly in Form 1, and hypophosphorylated pRb bind an E2F DNA binding site; p130 complexes E2F-4, whereas pRb binds both E2F-4 and E2F-1. The phosphorylated forms of E2F-4 that bind to the E2F DNA site are different from hyperphosphorylated E2F-4, which predominates in primary hemopoietic cells in G 0 . We conclude that although cell cycle arrest induced by α-IFN may be mediated in part by formation of a complex containing p130 and E2F-4, α-IFN does not induce hyperphosphorylation of E2F-4, which characterizes primary hemopoietic cells in G 0 .