Project description:Among the collection of chromatin modifications that influence its function and structure, the substitution of canonical histones by the so-called histone variants is one of the most prominent actions. Since crucial meiotic transactions are modulated by chromatin, here we investigate the functional contribution of the H2A.Z histone variant during both unperturbed meiosis and upon challenging conditions where the meiotic recombination checkpoint is triggered in budding yeast by the absence of the synaptonemal complex component Zip1. We have found that H2A.Z localizes to meiotic chromosomes in an SWR1-dependent manner. Although meiotic recombination is not substantially altered, the htz1 mutant (lacking H2A.Z) shows slower meiotic progression, impaired sporulation and reduced spore viability. These phenotypes are likely accounted for by the misregulation of meiotic gene expression landscape observed in htz1. In the zip1 mutant, the absence of H2A.Z results in a tighter meiotic arrest imposed by the meiotic recombination checkpoint. We have found that Mec1-dependent Hop1-T318 phosphorylation and the ensuing Mek1 activation are not significantly altered in zip1 htz1; however, downstream checkpoint targets, such as the meiosis I-promoting factors Ndt80, Cdc5 and Clb1, are drastically down-regulated. The study of the checkpoint response in zip1 htz1 has also allowed us to reveal the existence of an additional function of the Swe1 kinase, independent of CDK inhibitory phosphorylation, which is relevant to restrain meiotic cell cycle progression. In summary, our study shows that the H2A.Z histone variant impacts various aspects of meiotic development adding further insight into the relevance of chromatin dynamics for accurate gametogenesis.
Project description:Iron is an essential cofactor for enzymes involved in numerous cellular processes. We analyzed the metabolomes and transcriptomes of yeast grown in iron-rich and iron-poor media to determine which biosynthetic processes are altered when iron availability falls.
Project description:Total RNA samples from three replicate cultures of wild type and mutant yeast strains was isolated and expression profile done using Affymetrix arrays. Comparsion between the samples indicate how mutation in a single amino acid residue in histone H4 (H4R45H) affects gene expression in yeast. Such a mutation in histone H4 is known to generate a specific class of mutants called SWI/SNF independent (SIN) mutants, and the mutants were identified by their ability to carry out transcription in the absence of yeast chromatin remodeling complex SWI/SNF. SIN mutations are known to affect higher order chromatin structure and the comparative expression profile would help identification of genes which get affected by such altered chromatin landscape. Keywords: mutant analysis
