title: Inhibition of cell proliferation by the Mad1 transcriptional repressor.
abstract: Mad1 is a basic helix-loop-helix-leucine zipper protein that is induced upon differentiation of a number of distinct cell types. Mad1 dimerizes with Max and recognizes the same DNA sequences as do Myc:Max dimers. However, Mad1 and Myc appear to have opposing functions. Myc:Max heterodimers activate transcription while Mad:Max heterodimers repress transcription from the same promoter. In addition Mad1 has been shown to block the oncogenic activity of Myc. Here we show that ectopic expression of Mad1 inhibits the proliferative response of 3T3 cells to signaling through the colony-stimulating factor-1 (CSF-1) receptor. The ability of over-expressed Myc and cyclin D1 to complement the mutant CSF-1 receptor Y809F (containing a Y-to-F mutation at position 809) is also inhibited by Mad1. Cell cycle analysis of proliferating 3T3 cells transfected with Mad1 demonstrates a significant decrease in the fraction of cells in the S and G2/M phases and a concomitant increase in the fraction of G1 phase cells, indicating that Mad1 negatively influences cell cycle progression from the G1 to the S phase. Mutations in Mad1 which inhibit its activity as a transcription repressor also result in loss of Mad1 cell cycle inhibitory activity. Thus, the ability of Mad1 to inhibit cell cycle progression is tightly coupled to its function as a transcriptional repressor.
authors.affiliation: Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Roussel
authors.forename: R A
authors.initials: RA
authors.lastname: Ashmun
authors.forename: C J
authors.initials: CJ
authors.lastname: Sherr
authors.forename: R N
authors.initials: RN
authors.lastname: Eisenman
authors.forename: D E
authors.initials: DE
authors.lastname: Ayer
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002352:Carrier Proteins; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects / Q000235:genetics*; D019938:Cyclin D1; D016213:Cyclins / Q000494:pharmacology; D006801:Humans; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics*; D015513:Oncogene Proteins / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics*; D017354:Point Mutation; D016271:Proto-Oncogene Proteins c-myc / Q000494:pharmacology; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D016213:Cyclins; C501384:MAD1L1 protein, human; C501385:Mad1l1 protein, mouse; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D010750:Phosphoproteins; D016271:Proto-Oncogene Proteins c-myc; D012097:Repressor Proteins; D019938:Cyclin D1; D016173:Macrophage Colony-Stimulating Factor; D016186:Receptor, Macrophage Colony-Stimulating Factor