Yeast Recombination Enhancer Is Stimulated by Transcription Activation

Abstract

Saccharomyces cerevisiae mating type switching is a gene conversion event that exhibits donor preference. MAT a cells choose HMLα for recombination, and MATα cells choose HMR a. Donor preference is controlled by the recombination enhancer (RE), located between HMLα and MAT a on the left arm of chromosome III. A number of a-cell specific noncoding RNAs are transcribed from the RE locus. Mcm1 and Fkh1 regulate RE activity in a cells. Here we show that Mcm1 binding is required for both the transcription of the noncoding RNAs and Fkh1 binding. This requirement can be bypassed by inserting another promoter into the RE. Moreover, the insertion of this promoter increases donor preference and opens the chromatin structure around the conserved domains of RE. Additionally, we determined that the level of Fkh1 binding positively correlates with the level of donor preference. We conclude that the role of Mcm1 in RE is to open chromatin around the conserved domains and activate transcription; this facilitates Fkh1 binding and the level of this binding determines the level of donor preference.

ACKNOWLEDGMENTS

This work was supported by a National Institutes of Health grant to R.T.S. (GM 52311) and the Stowers Institute for Medical Research.

We thank Jim Haber for yeast strains and the members of the Simpson and Workman laboratories for discussions.