MARCKS protein is transcriptionally down-regulated in v-Src-transformed BALB/c 3T3 cells.
Activation of protein kinase C (PKC) by tumor-promoting phorbol esters leads to the phosphorylation of an 80-kilodalton PKC substrate (known as MARCKS) in murine fibroblasts. In BALB/c 3T3 cells stably transformed by v-Src, phorbol esters were unable to induce phosphorylation of MARCKS. Western blot analysis and in vitro kinase assays showed that both PKC protein levels and kinase activity were unchanged in v-Src-transformed relative to the parental nontransformed BALB/c 3T3 cells. However, MARCKS protein levels were reduced in v-Src-transformed cells relative to nontransformed cells. MARCKS RNA levels were also correspondingly reduced in v-Src-transformed cells. Nuclear "run-on" assays showed decreased transcription of MARCKS in v-Src-transformed cells. Thus, the absence of MARCKS in v-Src-transformed cells could be explained by a down-regulation of MARCKS transcription. Inhibiting the protein tyrosine kinase activity of v-Src with herbimycin A restored MARCKS RNA levels, MARCKS transcription, and MARCKS protein, suggesting that down-regulation of MARCKS in v-Src-transformed BALB/c 3T3 cells is a direct effect of v-Src.
Institute for Biomolecular Structure and Function, Hunter College, City University of New York, New York 10021.
C K
CK
Joseph
S A
SA
Qureshi
D J
DJ
Wallace
D A
DA
Foster
D016475:3T3 Cells; D000818:Animals; D016227:Benzoquinones; D015152:Blotting, Northern; D015153:Blotting, Western; D002461:Cell Line, Transformed; D015536:Down-Regulation; D015870:Gene Expression / Q000187:drug effects; D016391:Genes, src; D047908:Intracellular Signaling Peptides and Proteins; D047029:Lactams, Macrocyclic; D008565:Membrane Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D012313:RNA / Q000235:genetics; D017828:Rifabutin / Q000031:analogs & derivatives; D014158:Transcription, Genetic
D016227:Benzoquinones; D047908:Intracellular Signaling Peptides and Proteins; D047029:Lactams, Macrocyclic; C000619711:Marcks protein, mouse; D008565:Membrane Proteins; D011506:Proteins; D011809:Quinones; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D017828:Rifabutin; D012313:RNA; C020754:herbimycin; D011493:Protein Kinase C