| Autor: |
Johnson TK; Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA., Schweppe RE, Septer J, Lewis RE |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of biological chemistry [J Biol Chem] 1999 Dec 17; Vol. 274 (51), pp. 36741-9. |
| DOI: |
10.1074/jbc.274.51.36741 |
| Abstrakt: |
The transcription factor B-Myb is a cell cycle-regulated phosphoprotein and a potent regulator of cell cycle progression. Previous studies demonstrated that B-Myb was phosphorylated at the onset of S phase, suggesting that it could be due to cyclin-dependent kinases. We identified 10 B-Myb phosphorylation sites by automated peptide radiosequencing of tryptic phosphopeptides derived from in vivo (32)P-labeled B-Myb. Each B-Myb phosphorylation site contained a phosphoserine or phosphothreonine followed by a proline, suggesting that this phosphorylation is due to a proline-directed kinase. Cyclin A-Cdk2 and cyclin E-Cdk2 complexes each phosphorylated B-Myb in a cell-free system on the same sites as in intact cells. Furthermore, the ability of B-Myb to activate a reporter plasmid was enhanced by the cotransfection of cyclin A, whereas mutagenesis of the 10 identified phosphorylation sites from B-Myb blocked the effect of cyclin A coexpression. Additional analysis revealed that the effect of phosphorylation on B-Myb transactivation potential was enhanced by phosphorylation sites in its carboxyl-terminal half. One phosphorylation site (Ser(581)) appeared to negatively regulate DNA binding, as mutation of this site enhanced the ability of B-Myb to bind a Myb-binding sequence. These data suggest that B-Myb is a target for phosphorylation by cyclin-Cdk2 and that phosphorylation of B-Myb regulates its transcriptional activity. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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