TRANSCRIPTION OF THE E2F-1 GENE IS RENDERED CELL-CYCLE DEPENDENT BY E2F DNA-BINDING SITES WITHIN ITS PROMOTER

The cell cycle-regulatory transcription factor E2F-1 is regulated by i nteractions with proteins such as the retinoblastoma gene product and by cell cycle-dependent alterations in E2F-1 mRNA abundance. To better understand this latter phenomenon, we have isolated the human E2F-1 p romoter. The human E2F-1 promoter, fused to a luciferase cDNA, gave ri se to cell cycle-dependent luciferase activity upon transfection into mammalian cells in a manner Which paralleled previously reported chang es in E2F-1 mRNA abundance. The E2F-1 promoter contains four potential E2F-binding sites organized as two imperfect palindromes. Gel shift a nd transactivation studies suggested that these sites can bind to E2F in vitro and in vivo. Mutation of the two E2F palindromes abolished th e cell cycle dependence of the E2F-1 promoter. Thus, E2F-1 appears to be regulated at the level of transcription, and this regulation is due , at least in part, to binding of one or more E2F family members to th e E2F-1 promoter.