THE TATA-LESS PROMOTER OF MOUSE RIBONUCLEOTIDE REDUCTASE R1 GENE CONTAINS A TFII-I BINDING INITIATOR ELEMENT ESSENTIAL FOR CELL-CYCLE-REGULATED TRANSCRIPTION

Mammalian ribonucleotide reductase shows S-phase specific expression a nd consists of two non-identical subunits, proteins R1 (large subunit) and R2 (small subunit), A comparison between the human and mouse TATA -less R1 gene promoters revealed four highly conserved DNA regions, wh ile the remaining sequence showed a low degree of conservation. Two re gions, alpha and beta were earlier identified as protein binding regio ns in the mouse R1 promoter by using DNase footprinting technique, The two new regions are located to the transcription start and to a DNA s equence about 40 base pairs downstream from the start, Gel shift assay s using TFII-I antibodies and competition with an oligonucleotide repr esenting the terminal deoxynucleotidyl transferase initiator element i dentified the start region as a TFII-I binding initiator element, The conserved downstream region, called gamma, also formed specific DNA-pr otein complexes in gel shift assays, Functional studies, using synchro nized cells stably transformed by R1 promoter-luciferase reporter gene constructs, indicated that the initiator and the gamma elements toget her were necessary for cell cycle-regulated R1 promoter activity. Earl ier published data, indicating Sp1 binding to the R1 alpha/beta region s, could not be confirmed, suggesting that the R1 initiator element ma y function independent of Sp1.