Cell adhesion regulates pro-alpha 1(I) collagen mRNA stability and transcription in mouse fibroblasts.
Adhesive interactions are important modulators of cellular phenotype. Previously, we demonstrated that quiescent, suspension-arrested cells are not equivalent to density-arrested cells in their patterns of gene expression (Dhawan, J., and Farmer, S.R. (1990) J. Biol. Chem. 265, 9015-9021). In particular, pro-alpha 1(I) collagen expression depended strongly on the extent of cell adhesion. In this paper, we demonstrate that the adhesion-induced rise in collagen gene expression is due to regulation at multiple levels. Steady state levels of pro-alpha 1(I) collagen mRNA increased up to 10-fold by 6 h after replating suspended cells, and this rise is blocked by inhibition of protein synthesis. Transcription of the pro-alpha 1(I) collagen gene was measured by run-on assay as well as by activation of a rat alpha 1(I) promoter-chloramphenicol acetyltransferase reporter gene construct. Both assays reveal a 5-fold depression of pro-alpha 1(I) collagen gene transcription in suspended cells. Reattachment of suspended cells resulted in the activation of alpha 1(I) gene transcription by 2-h postreplating, reaching a 3-5-fold level of induction by 18 h. The pro-alpha 1(I) collagen mRNA was substantially more labile in suspended cells than in adherent cells (t1/2 values of approximately 2 h in nonadherent cells and greater than 8 h in exponentially growing or density-arrested cells). Furthermore, reattachment of suspended cells for 18 h resulted in a stabilization of collagen mRNA. We conclude that cell adhesion regulates pro-alpha 1(I) collagen gene expression selectively and at transcriptional and posttranscriptional sites.
Dhawan
J
J
Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118.
Lichtler
A C
AC
Rowe
D W
DW
Farmer
S R
SR
D000818:Animals; D015152:Blotting, Northern; D002448:Cell Adhesion; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D003001:Cloning, Molecular; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D005353:Fibronectins / Q000235:genetics; D005786:Gene Expression Regulation; D006207:Half-Life; D007700:Kinetics; D051379:Mice; D011347:Procollagen / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism*; D014158:Transcription, Genetic
D005353:Fibronectins; D011347:Procollagen; D012333:RNA, Messenger; D003094:Collagen; D003513:Cycloheximide; D015500:Chloramphenicol O-Acetyltransferase