REGULATION OF THE RETINOBLASTOMA ANTIONCOGENE IN AGING HUMAN-DIPLOID FIBROBLASTS

Cell cycle expression of the retinoblastoma (RB) gene was investigated in young and aging IMR 90 human diploid fibroblasts and in the immortalized but untransformed A31 BALB/c 3T3 mouse fibroblasts. RB RNA levels increased about 75% during late G1/S in both the young and old IMR 90 cells. Young and old cells had similar normalized amounts of RB RNA per cell. Kinase C activation did not stimulate RB transcription. The A31 cells showed a constant RB RNA level throughout G0/S. The data is consistent with the hypothesis that RB activity is regulated primarily post-transcriptionally and indicates that a change in the regulation of RB transcription is not part of the senescence phenomenon.