RING3 kinase transactivates promoters of cell cycle regulatory genes through E2F.
RING3 is a novel, nuclear-localized, serine-threonine kinase that has elevated activity in human leukemias. RING3 transforms NIH/3T3 cells and is activated by mitogenic signals, all of which suggest that it may play a role in cell cycle-responsive transcription. We tested this hypothesis with transient transfection of RING3 into fibroblasts and assayed transactivation of the promoters of cyclin D11 cyclin A, cyclin E, and dihydrofolate reductase (dhfr) genes. RING3 transactivates these promoters in a manner dependent on ras signaling. A kinase-deficient point mutant of RING3 does not transactivate. Mutational analysis of the dhfr promoter reveals that transactivation also depends on the presence of a functional E2F binding site. Furthermore, ectopic expression of Rb protein, a negative regulator of E2F activity, suppresses the RING3-dependent transactivation of this promoter. Consistent with a potential role of E2F in RING3-dependent transcription, anti-RING3 immunoaffinity chromatography or recombinant RING3 protein affinity chromatography of nuclear extracts copurified a protein complex that contains E2F-1 and E2F-2. These data suggest that RING3 is a potentially important regulator of E2F-dependent cell cycle genes.
Pubmed ID: 10965846 RIS Download
3T3 Cells | Animals | Carrier Proteins | Cell Cycle Proteins | Chromosomal Proteins, Non-Histone | Cyclins | DNA-Binding Proteins | E2F Transcription Factors | E2F1 Transcription Factor | Macromolecular Substances | Mice | Promoter Regions, Genetic | Protein-Serine-Threonine Kinases | Retinoblastoma-Binding Protein 1 | Time Factors | Transcription Factor DP1 | Transcription Factors | Transcriptional Activation