A cell cycle-responsive transcriptional control element and a negative control element in the gene encoding DNA polymerase alpha in Saccharomyces cerevisiae

Abstract

Transcription of the POL1 gene of Saccharomyces cerevisiae, which encodes DNA polymerase alpha, the DNA polymerase required for the initiation of DNA replication, has previously been shown to be cell cycle regulated. To understand how the POL1 gene senses cell cycle position, we have investigated the cis-acting elements that respond to the factors that govern cell cycle progression. In this report we demonstrate that a region of 54 nucleotides containing the repeated element ACGCGT, which conforms to an Mlu I restriction endonuclease recognition site, contains all information necessary for transcriptional activation and cell cycle responsiveness. Although oligonucleotides lacking either one or both of the repeated Mlu I sites can function as an upstream activating sequence, the presence of at least one Mlu I site stimulates expression and, moreover, is absolutely essential for cell cycle regulation. A synthetic oligonucleotide corresponding to a 19-base-pair sequence in the POL1 promoter containing one Mlu I site can function as an autonomous cell cycle-responsive upstream element (upstream activation sequence) with temporal regulation indistinguishable from that previously described for the POL1 gene. Thus, the Mlu I site is an essential part of a cis-acting element responsible for the observed periodic activation. This sequence differs from previously defined cell cycle-responsive transcriptional control elements in the yeast HO endonuclease and histone genes. We also present evidence for a negative regulatory element in the 5' flanking region of the Mlu I upstream activation sequence.