Regulation of the cyclin E gene by transcription factor E2F1.

A variety of results point to the transcription factor E2F as a critical determinant of the G1/S-phase transition during the cell cycle in mammalian cells, serving to activate the transcription of a group of genes that encode proteins necessary for DNA replication. In addition, E2F activity appears to be directly regulated by the action of retinoblastoma protein (RB) and RB-related proteins and indirectly regulated through the action of G1 cyclins and associated kinases. We now show that the accumulation of G1 cyclins is regulated by E2F1. E2F binding sites are found in both the cyclin E and cyclin D1 promoters, both promoters are activated by E2F gene products, and at least for cyclin E, the E2F sites contribute to cell cycle-dependent control. Most important, the endogenous cyclin E gene is activated following expression of the E2F1 product encoded by a recombinant adenovirus vector. These results suggest the involvement of E2F1 and cyclin E in an autoregulatory loop that governs the accumulation of critical activities affecting the progression of cells through G1. IMAGES: