| First Author | Wu A | Year | 2005 |
| Journal | J Biol Chem | Volume | 280 |
| Issue | 4 | Pages | 2863-72 |
| PubMed ID | 15533945 | Mgi Jnum | J:96488 |
| Mgi Id | MGI:3530711 | Doi | 10.1074/jbc.M406138200 |
| Citation | Wu A, et al. (2005) Regulation of upstream binding factor 1 activity by insulin-like growth factor I receptor signaling. J Biol Chem 280(4):2863-72 |
| abstractText | The upstream binding factor 1 (UBF1) is one of the proteins in a complex that regulates the activity of RNA polymerase I, which controls the rate of ribosomal RNA (rRNA) synthesis. We have shown previously that insulin receptor substrate-1 (IRS-1) can translocate to the nuclei and nucleoli of cells and bind UBF1. We report here that activation of the type I insulin-like growth factor receptor (IGF-IR) by IGF-I increases transcription from the ribosomal DNA (rDNA) promoter in both myeloid cells and mouse fibroblasts. The increased activity of the rDNA promoter is accompanied by increased phosphorylation of UBF1, a requirement for UBF1 activation. Phosphorylation occurs on a number of UBF1 peptides, most prominently on the highly acidic, serine-rich C terminus. In myeloid cells (but not in mouse embryo fibroblasts) IRS-1 signaling stabilizes the levels of UBF1 protein. These findings demonstrate that IGF-IR signaling can increase the activity of UBF1 and transcription from the rDNA promoter, providing one explanation for the reported effects of the IGF/IRS-1 axis on cell and body size in animals and cells in culture. |
