The DNA repair genes RAD54 and UNG1 are cell cycle regulated in budding yeast but MCB promoter elements have no essential role in the DNA damage response.

The DNA repair genes RAD54 and UNG1 have MCB elements in their promoters and are shown to be cell cycle regulated. Their transcripts are coordinately expressed with RNR1, ribonucleotide reductase, a MCB-regulated gene known to be expressed in late G1. However, no evidence was obtained for a direct role of MCB elements in DNA repair. Of the proteins that bind and activate MCB elements, only mutations in SWI6 have a defect in DNA repair, showing significant sensitivity to methyl methane sulphonate. Furthermore, analysis of the CDC9 promoter indicates that MCB elements are not required for the induction of the gene by ultraviolet light irradiation. These promoter elements may not respond directly to DNA damage but may have a role in enhancing the induction response.