Regulation and activity of the retinoblastoma protein family in growth factor-deprived and TGF(beta)-treated keratinocytes.
The retinoblastoma protein (pRB) and the pRB-related pocket proteins p130 and p107, when bound to DNA via the E2F family of transcription factors, suppress transcription and through this may mediate growth arrest. We show here that in HaCat cells arrested by treatment with TGFbeta the only pocket protein associating with DNA-bound E2F is pRB. This contrasts the situation in HaCat cells arrested via growth factor withdrawal, where we find that both pRB and p130 can bind. The above implies that p130 participates in regulating E2F-dependent genes upon growth factor deprivation but not upon TGFbeta arrest. More importantly perhaps, in TGFbeta-arrested cells pRB alone in association with its partner E2Fs may be in charge and sufficient to control E2F-dependent gene transcription. Although p130 is not associated with a DNA-binding E2F complex in TGFbeta-treated cells, it is present in such cells in its underphosphorylated form. We provide evidence for a serum-induced process that may regulate p130 by a mechanism independent of p130 hyperphosphorylation.
Belbrahem
A
A
The Institute of Cancer Research, Chester Beatty Laboratories, London, United Kingdom.
Godden-Kent
D
D
Mittnacht
S
S
D001483:Base Sequence; D001798:Blood Proteins / Q000494:pharmacology; D015153:Blotting, Western; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002461:Cell Line, Transformed / Q000187:drug effects / Q000502:physiology; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D050684:E2F Transcription Factors; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000502:physiology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000235:genetics*; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D001798:Blood Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D011500:Protein Synthesis Inhibitors; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D004004:Dichlororibofuranosylbenzimidazole; D004247:DNA; D003513:Cycloheximide