Diverse and dynamic forms of gene regulation by the S. cerevisiae histone methyltransferase Set1.

Gene transcription is an essential and highly regulated process. In eukaryotic cells, the structural organization of nucleosomes with DNA wrapped around histone proteins impedes transcription. Chromatin remodelers, transcription factors, co-activators, and histone-modifying enzymes work together to make DNA accessible to RNA polymerase.

Histone 3 lysine 4 monomethylation supports activation of transcription in S. cerevisiae during nutrient stress.

Mono-methylation of the fourth lysine on the N-terminal tail of histone H3 was found to support the induction of RNA polymerase II transcription in S. cerevisiae during nutrient stress. In S.

Catalytic and functional roles of conserved amino acids in the SET domain of the S. cerevisiae lysine methyltransferase Set1.

In S. cerevisiae, the lysine methyltransferase Set1 is a member of the multiprotein complex COMPASS. Set1 catalyzes mono-, di- and trimethylation of the fourth residue, lysine 4, of histone H3 using methyl groups from S-adenosylmethionine, and requires a subset of COMPASS proteins for this activity.

Calorie restriction effects on silencing and recombination at the yeast rDNA.

Aging research has developed rapidly over the past decade, identifying individual genes and molecular mechanisms of the aging process through the use of model organisms and high throughput technologies. Calorie restriction (CR) is the most widely researched environmental manipulation that extends lifespan. Activation of the NAD(+)-dependent protein deacetylase Sir2 (Silent Information Regulator 2) has been proposed to mediate the beneficial effects of CR in the budding yeast Saccharomyces cerevisiae, as well as other organisms.

An increase in mitochondrial DNA promotes nuclear DNA replication in yeast.

Coordination between cellular metabolism and DNA replication determines when cells initiate division. It has been assumed that metabolism only plays a permissive role in cell division. While blocking metabolism arrests cell division, it is not known whether an up-regulation of metabolic reactions accelerates cell cycle transitions.

Linker histone H1 represses recombination at the ribosomal DNA locus in the budding yeast Saccharomyces cerevisiae.

Several epigenetic phenomena occur at ribosomal DNA loci in eukaryotic cells, including the silencing of Pol I and Pol II transcribed genes, silencing of replication origins and repression of recombination. In Saccharomyces cerevisiae, studies focusing on the silencing of Pol II transcription and genetic recombination at the ribosomal DNA locus (rDNA) have provided insight into the mechanisms through which chromatin and chromatin-associated factors regulate gene expression and chromosome stability. The core histones, H2A, H2B, H3 and H4, the fundamental building blocks of chromatin, have been shown to regulate silent chromatin at the rDNA; however, the function of the linker histone H1 has not been well characterized.

Isw2 regulates gene silencing at the ribosomal DNA locus in Saccharomyces cerevisiae.

Three heterochromatin-like domains have been identified in Saccharomyces cerevisiae that are refractory to transcription by Pol II, the silent mating-type loci, telomeres and the ribosomal DNA. Previous work has shown that chromatin remodelers can regulate silent chromatin. Here, we report the findings of an investigation into the role of ISW2 in transcriptional silencing at the rDNA.

Isw1 acts independently of the Isw1a and Isw1b complexes in regulating transcriptional silencing at the ribosomal DNA locus in Saccharomyces cerevisiae.

Transcriptional silencing of Pol II-transcribed genes in Saccharomyces cerevisiae occurs at the HM loci, telomeres and ribosomal DNA (rDNA) locus. Gene silencing at these loci requires histone-modifying enzymes as well as factors that regulate local chromatin structure. Previous work has shown that the ATP-dependent chromatin remodeling protein Isw1 is required for silencing of a marker gene inserted at the HMR locus, but not at telomeres.

Sir2 represses endogenous polymerase II transcription units in the ribosomal DNA nontranscribed spacer.

Silencing at the rDNA, HM loci, and telomeres in Saccharomyces cerevisiae requires histone-modifying enzymes to create chromatin domains that are refractory to recombination and RNA polymerase II transcription machineries. To explore how the silencing factor Sir2 regulates the composition and function of chromatin at the rDNA, the association of histones and RNA polymerase II with the rDNA was measured by chromatin immunoprecipitation. We found that Sir2 regulates not only the levels of K4-methylated histone H3 at the rDNA but also the levels of total histone H3 and RNA polymerase II.

The requirements for COMPASS and Paf1 in transcriptional silencing and methylation of histone H3 in Saccharomyces cerevisiae.

The Set1-containing complex, COMPASS, methylates histone H3 on lysine 4 (K4) in Saccharomyces cerevisiae. Despite the preferential association of K4-trimethylated H3 with regions of the genome that are transcribed by RNA polymerase II, transcriptional silencing is one of the few cases in S. cerevisiae where histone-methylation defects have a clear effect on gene expression.

Evidence that Set1, a factor required for methylation of histone H3, regulates rDNA silencing in S. cerevisiae by a Sir2-independent mechanism.

Several types of histone modifications have been shown to control transcription. Recent evidence suggests that specific combinations of these modifications determine particular transcription patterns. The histone modifications most recently shown to play critical roles in transcription are arginine-specific and lysine-specific methylation.