Repression of c-Myc responsive genes in cycling cells causes G1 arrest through reduction of cyclin E/CDK2 kinase activity.
The c-myc gene encodes a sequence-specific DNA binding protein involved in proliferation and oncogenesis. Activation of c-myc expression in quiescent cells is sufficient to mediate cell cycle entry, whereas inhibition of c-myc expression causes cycling cells to withdraw from the cell cycle. To search for components of the cell cycle machinery that are targets of c-Myc, we have made a mutant c-Myc protein, named MadMyc, that actively represses c-myc target genes. Expression of MadMyc in cycling NIH3T3 cells causes a significant accumulation of cells in G1. The MadMyc-induced G1 arrest is rescued by ectopic expression of cyclin E/CDK2 and cyclin D1/ CDK4, but not by Cdc25A, a known cell cycle target of c-Myc. The MadMyc G1 arrest does not require the presence of a functional retinoblastoma protein and is associated with a strong reduction in cyclin E/CDK2 kinase activity in arrested cells. MadMyc does not cause alterations in the expression levels of cyclin E, CDK2, p27kip1, cyclin D1 or CDK4 in G1-arrested cells. These data indicate that inhibition of c-Myc activity in exponentially growing cells leads to G1 arrest through loss of cyclin E-associated kinase activity.
Berns
K
K
Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Hijmans
E M
EM
Bernards
R
R
D000818:Animals; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase / Q000235:genetics*; D005786:Gene Expression Regulation; D016259:Genes, myc; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism
D019927:Cyclin E; D016271:Proto-Oncogene Proteins c-myc; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases