A single heterochromatin boundary element imposes position-independent antisilencing activity in Saccharomyces cerevisiae minichromosomes.

Chromatin boundary elements serve as cis-acting regulatory DNA signals required to protect genes from the effects of the neighboring heterochromatin. In the yeast genome, boundary elements act by establishing barriers for heterochromatin spreading and are sufficient to protect a reporter gene from transcriptional silencing when inserted between the silencer and the reporter gene. Here we dissected functional topography of silencers and boundary elements within circular minichromosomes in Saccharomyces cerevisiae.

Cohesin interaction with centromeric minichromosomes shows a multi-complex rod-shaped structure.

Cohesin is the protein complex responsible for maintaining sister chromatid cohesion. Cohesin interacts with centromeres and specific loci along chromosome arms known as Chromosome Attachment Regions (CARs). The cohesin holocomplex contains four subunits.

The DNA repair protein yKu80 regulates the function of recombination enhancer during yeast mating type switching.

Recombination enhancer (RE) is essential for regulating donor preference during yeast mating type switching. In this study, by using minichromosome affinity purification (MAP) and mass spectrometry, we found that yeast Ku80p is associated with RE in MATa cells. Chromatin immunoprecipitation assays confirmed its occupancy in vivo.

Yeast recombination enhancer is stimulated by transcription activation.

Saccharomyces cerevisiae mating type switching is a gene conversion event that exhibits donor preference. MATa cells choose HMLalpha for recombination, and MATalpha cells choose HMRa. Donor preference is controlled by the recombination enhancer (RE), located between HMLalpha and MATa on the left arm of chromosome III.

Global chromatin structure of 45,000 base pairs of chromosome III in a- and alpha-cell yeast and during mating-type switching.

Directionality of yeast mating-type switching has been attributed to differences in chromatin structure for the left arm of chromosome III. We have mapped the structure of approximately 45 kbp of the left arm of chromosome III in a and alpha cells in logarithmically growing cultures and in a cells during switching. Distinctive features of chromatin structure were the occurrence of DNase I-hypersensitive sites in the promoter region of nearly every gene and some replication origins and the presence of extended regions of positioned nucleosomes in approximately 25% of the open reading frames.