Early induction of ribonucleotide reductase gene expression by transforming growth factor beta 1 in malignant H-ras transformed cell lines.
Previous investigations have indicated that the suppression of proliferation by transforming growth factor (TGF) beta 1 is often lost upon cellular transformation, and that proliferation of some tumors is stimulated by TGF-beta. The present study provides the first observation of a link between TGF-beta 1 regulation of this process and alterations in the expression of ribonucleotide reductase, a highly controlled rate-limiting step in DNA synthesis. A series of radiation and T24-H-ras-transformed mouse 10T1/2 cell lines exhibiting increasing malignant potential was evaluated for TGF-beta 1 induced alterations in ribonucleotide reductase M1 and M2 gene expression. Early increases in M1 and/or M2 message and protein levels were observed only in malignant cell lines. The TGF-beta 1 induced changes in M1 and/or M2 gene expression occurred prior to any detectable changes in the rates of DNA synthesis, supporting the novel concept that ribonucleotide reductase gene expression can be elevated by TGF-beta 1 without altering the proportion of cells in S phase. T24-H-ras-transformed 10T1/2 cells were transfected with a plasmid containing the coding region of TGF-beta 1 under the control of a zinc-sensitive metallothionein promoter. When these cells were cultured in the presence of zinc, a large induction of TGF-beta 1 message was observed within 1 h. Both M1 and M2 genes were also induced, with increased mRNA levels appearing 2 h after zinc treatment, or 1 h after TGF-beta 1 message levels were clearly elevated. In total, the data suggests a mechanism of autocrine stimulation of malignant cells by TGF-beta 1, in which early alterations in the regulation of ribonucleotide reductase may play an important role.
Hurta
R A
RA
Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Canada.
Samuel
S K
SK
Greenberg
A H
AH
Wright
J A
JA
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D004261:DNA Replication / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D011905:Genes, ras; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D051379:Mice; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D012264:Ribonucleotide Reductases / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D012264:Ribonucleotide Reductases; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases