title: Transforming growth factor-beta1 modulates p107 function in myeloid cells: correlation with cell cycle progression.
abstract: Transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of hematopoietic cell growth. Here we report that TGF-beta1 signals inhibition of IL-3-dependent 32D-123 murine myeloid cell growth by modulating the activities of cyclin E and cyclin-dependent kinase 2 (cdk2) proteins and their complex formation in the G1 phase of the cell cycle. Whereas the cyclin E protein was hyperphosphorylated in TGF-beta1 treated cells, TGF-beta1 decreased both the phosphorylation of cdk2 and the kinase activity of the cyclin E-cdk2 complex. Decreased cyclin E-cdk2 kinase activity correlated with decreased phosphorylation of the retinoblastoma-related protein p107. In support of these observations, transient overexpression of p107 inhibited the proliferation of the myeloid cells, and expression of antisense oligodeoxynucleotides to p107 mRNA blocked TGF-beta1 inhibition of myeloid cell growth. Furthermore, as reported previously, in 32D-123 TGF-beta1 treated cells, c-Myc protein expression was decreased. TGF-beta1 increased the binding of p107 to the transcription factor E2F, leading to decreased c-Myc protein levels. p107 inhibited E2F transactivation activity and was also found to bind the c-Myc protein, suggesting p107 negative regulation of c-Myc protein function. These studies demonstrate the modulation of p107 function by TGF-beta1 and suggest a novel mechanism by which TGF-beta1 blocks cell cycle progression in myeloid cells.
authors.affiliation: Biological Carcinogenesis and Development Program, SAIC Frederick, Maryland, 21702, USA.
authors.forename: O S
authors.initials: OS
authors.lastname: Bang
authors.forename: F W
authors.initials: FW
authors.lastname: Ruscetti
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
authors.forename: S J
authors.initials: SJ
authors.lastname: Kim
authors.forename: M C
authors.initials: MC
authors.lastname: Birchenall-Roberts
mesh_terms: D000818:Animals; D001853:Bone Marrow; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D016213:Cyclins / Q000096:biosynthesis; D015870:Gene Expression / Q000187:drug effects; D006412:Hematopoietic Stem Cells / Q000166:cytology; D007377:Interleukin-3 / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000502:physiology; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D050720:Retinoblastoma-Like Protein p107; D015398:Signal Transduction; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D016213:Cyclins; D007377:Interleukin-3; D009687:Nuclear Proteins; C489485:Rbl1 protein, mouse; D011993:Recombinant Fusion Proteins; D050720:Retinoblastoma-Like Protein p107; D016212:Transforming Growth Factor beta; D015500:Chloramphenicol O-Acetyltransferase; D011494:Protein Kinases