CHF: a novel factor binding to cyclin A CHR corepressor element.
Cell cycle modulation of cyclin A expression is due to the periodic relief of a transcriptional repression mediated by a bipartite negative DNA regulatory region. The 5' element (Cell Cycle Responsive Element: CCRE; cell Cycle Dependent Element: CDE) is clearly occupied in a cyclic manner in vivo, whereas the 3' element, whose sequence is shared by B-myb, cdc25C and cdc2 genes (cell Cycle gene Homology Region: CHR), is involved in more subtle interactions. Mutation of either element results in complete deregulation of cyclin A promoter activity. Whereas some reports claim that E2F/DP can bind to the CCRE/CDE, the nature of the protein(s) interacting with the CHR is unknown. In the present work we have characterized an activity present in quiescent cells and absent in cells blocked in S phase, which binds specifically to cyclin A CHR, but not to B-myb, or to cdc25C, or to cdc2 CHRs. A 90 kD protein, named CHF (cyclin A CHR binding factor), has been identified through preparative electrophoresis and UV crosslinking experiments. In order to address in more functional terms the binding of CHF to cyclin A CHR, we developed in vitro and in vivo oligonucleotide competition assays. Both in vitro transcription and in vivo microinjection experiments demonstrate that a functional difference exists between the composite CCRE/CDE-CHR repressor regions of cell cycle regulated genes such as cyclin A and cdc25C.
Philips
A
A
Institut de Génétique Moléculaire, CNRS, UMR 5535, Montpellier, France.
Chambeyron
S
S
Lamb
N
N
Vié
A
A
Blanchard
J M
JM
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002453:Cell Cycle / Q000235:genetics*; D002850:Chromatography, Gel; D019925:Cyclin A / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D046911:Macromolecular Substances; D051379:Mice; D008845:Microinjections; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D016192:Resting Phase, Cell Cycle; D016196:S Phase / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D014157:Transcription Factors / Q000302:isolation & purification* / Q000378:metabolism; D014158:Transcription, Genetic
D019925:Cyclin A; D046911:Macromolecular Substances; D014157:Transcription Factors; D006918:Hydroxyurea