A repetitive DNA sequence that confers cell-cycle START (CDC28)-dependent transcription of the HO gene in yeast.

The interconversion of mating types in yeast is initiated by an endonuclease encoded by the HO gene. HO is transcribed only transiently during the G1 phase of the cell cycle, as cells undergo START. A deletion analysis of HO 5'-flanking DNA suggests that there must be multiple copies of the sequence that confers START-specific transcription in the interval from -150 to -900. Analysis of this interval revealed 10 occurrences of sequences that closely match the consensus Pur N N Pyr C A C G A4. To test whether these sequences are the putative cell-cycle control elements, synthetically derived copies of the consensus were inserted at the break points of constitutive deletions and shown to restore START-dependent cell-cycle control.