Retinoblastoma susceptibility gene product (pRb) and p107 functionally separate the requirements for serum and anchorage in the cell cycle G1-phase.
Growth factors and cell anchorage are both required for cell cycle G(1)-phase progression, but it is unclear whether their function is mediated through the same set of cell cycle components and whether they are both required during the same periods of time. We separately analyzed the requirements of serum and anchorage during G(1)-phase progression and found that human dermal fibroblasts as well as wild type, pRb(-/-), and p107(-/-) mouse embryonic fibroblasts needed serum (growth factors) until mid-G(1)-phase but required cell anchorage until late G(1)-phase to be competent for S-phase entry. Importantly, however, pRb/p107 double-null mouse embryonic fibroblasts lacked serum requirement in mid-G(1)-phase but still required cell anchorage until late G(1)-phase to enter S-phase. Our results indicate that pRb and p107 do not constitute the last control point for extracellular factors during G(1)-phase progression, and they functionally separate the requirements for serum and cell anchorage in terms of involved cell cycle components.
Gad
Annica
A
Department of Laboratory Medicine, 141 86 Huddinge, Sweden.
Thullberg
Minna
M
Dannenberg
Jan-Hermen
JH
te Riele
Hein
H
Strömblad
Staffan
S
D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology*; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D056741:Cyclin D; D016213:Cyclins / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology*; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D012867:Skin / Q000166:cytology
D001798:Blood Proteins; D056741:Cyclin D; D016213:Cyclins; D009687:Nuclear Proteins; C493844:RBL1 protein, human; C489485:Rbl1 protein, mouse; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107