Rapid induction of competence formation is PDGF-isoform specific.
Platelet-derived growth factor (PDGF) stimulates the expression of a number of genes associated with entry of quiescent Balb/c-3T3 fibroblasts into the cell cycle. We determined that two of these genes, c-myc and c-fos, are induced equivalently in medium supplemented with platelet-poor plasma (PPP) and either PDGF-BB or PDGF-AA. The rate at which fibroblasts entered S phase was also similar in PDGF-BB- and AA-treated cells as was the expression of the late G1 gene, thymidine kinase (TK). However, PDGF-AA must be present for a period of 16 h to stimulate the proliferation of 90% of the cells, whereas PDGF-BB was required for only 4 h. Exposure of cells to PDGF-AA for 4 h, a time during which maximum expression of c-fos and c-myc occurred, only induced 20% of the cells in a quiescent population to enter the cell cycle. Therefore, PDGF-AA-mediated expression of the immediate early genes c-fos and c-myc may be necessary but is not sufficient to rapidly stimulate density-arrested Balb/c-3T3 fibroblasts into the competent state. Thus, these data suggest that PDGF-AA and PDGF-BB initiate traverse of the cell cycle by distinct mechanisms.
Coats
S R
SR
Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
Olson
J E
JE
Pledger
W J
WJ
D016475:3T3 Cells; D000818:Animals; D015152:Blotting, Northern; D002455:Cell Division / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D016762:Genes, fos; D016259:Genes, myc; D007700:Kinetics; D051379:Mice; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D011233:Precipitin Tests; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism
D010982:Platelet-Derived Growth Factor; D013937:Thymidine Kinase; D017479:Receptors, Platelet-Derived Growth Factor