Characterization of the Human RB1 Promoter and of Elements Involved in Transcriptional Regulation1

The retinoblastoma gene (RUl) is a recessive oncogene implicated in a number of human tumors. Although the RB1 gene is expressed in most proliferating cells, there is considerable evidence for the transcriptional regulation of this gene. Therefore, we have performed a detailed analysis of the regulatory elements in the promoter of the human RB1 gene. Deletion analysis of the 5’ upstream region determined the location of the basal promoter to be between -208 and -1 79 nucleotides relative to the translational start. This region contains essential binding sites for the transcription elements ATF and s u and potentially important sites for E2F and steroid hormone responsiveness but no TATA or CAAT boxes. Primer extension and RNase protection analysis identified two initiation sites at -1 76 and -1 28 base pairs, both downstream of the promoter. Cotransfection experiments revealed repression of the RIJi promoter by its protein produd pu u0R81#{149} This repression has been mapped to the core promoter region containing the E2Fbinding site; however, this site is not required for autorepression.