High-Resolution Structural Analysis of Chromatin at Specific Loci:Saccharomyces cerevisiaeSilent Mating-Type LocusHMRa

Anish Ravindra, Kerstin Weiss, Robert T. Simpson
1999 Molecular and Cellular Biology  
Genetic and biochemical evidence implicates chromatin structure in the silencing of the two quiescent mating-type loci near the telomeres of chromosome III in yeast. With high-resolution micrococcal nuclease mapping, we show that theHMRa locus has 12 precisely positioned nucleosomes spanning the distance between the E and I silencer elements. The nucleosomes are arranged in pairs with very short linkers; the pairs are separated from one another by longer linkers of ∼20 bp. Both the basic
more » ... erminal region of histone H4 and the silent information regulator protein Sir3p are necessary for the organized repressive chromatin structure of the silent locus. Compared toHMRa, only small differences in the availability of the TATA box are present for the promoter in the cassette at the activeMATa locus. Features of the chromatin structure of this silent locus compared to the previously studiedHMLα locus suggest differences in the mechanisms of silencing and may relate to donor selection during mating-type interconversion.
doi:10.1128/mcb.19.12.7944 pmid:10567520 pmcid:PMC84879 fatcat:uemdeigvlrezji2hotabzzesvi