Saccharomyces cerevisiae histone H2A Ser122 facilitates DNA repair.

Department of Biochemistry, University of Cambridge, UK.
Genetics (Impact Factor: 4.87). 07/2005; 170(2):543-53. DOI: 10.1534/genetics.104.038570
Source: PubMed

ABSTRACT DNA repair takes place in the context of chromatin. Recently, it has become apparent that proteins that make up and modulate chromatin structure are involved in the detection and repair of DNA lesions. We previously demonstrated that Ser129 in the carboxyl-terminal tail of yeast histone H2A is important for double-strand-break responses. By undertaking a systematic site-directed mutagenesis approach, we identified another histone H2A serine residue (Ser122) that is important for survival in the presence of DNA-damaging agents. We show that mutation of this residue does not affect DNA damage-dependent Rad53 phosphorylation or G(2)/M checkpoint responses. Interestingly, we find that yeast lacking H2A S122 are defective in their ability to sporulate. Finally, we demonstrate that H2A S122 provides a function distinct from that of H2A S129. These data demonstrate a role for H2A S122 in facilitating survival in the presence of DNA damage and suggest a potential role in mediating homologous recombination. The distinct roles of H2A S122 and S129 in mediating these responses suggest that chromatin components can provide specialized functions for distinct DNA repair and survival mechanisms and point toward the possibility of a complex DNA damage responsive histone code.


Available from: Jessica Downs, Oct 30, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Eukaryotes must package a large amount of DNA into the small space of a nucleus, while still being able to access necessary genes. Chromatin is the packaged form of DNA, in which DNA is wrapped around histone pro- teins to form the nucleosome, which is the smallest part of chromatin. There are four core histones: H2A, H2B, H3, and H4, and two copies of each histone in every nucleosome. Histones have flexible tail regions that include many amino acids that can be covalently modified. These modifications signal numer- ous cellular processes, including DNA repair. This study focused on histone H2A, in particular the modification on the serine 122 residue (S122). S122 is interesting because when it is mutated to an alanine (S122A mutant) the cells are more sensitive to many types of stress such as DNA damaging agents, like methyl methane sulfonate (MMS). To understand the role of H2A S122 in DNA double strand break repair we performed a suppressor screen, in which we rescued this sensitivity using a genomic library. We set up the suppressor screen by constructing and characterizing a strain of H2A S122A for the genetic screen. After strain construction we then compared the new S122A screen strain with an existing S122A strain to make sure the strain exhibited proper sensitivity to MMS. We then optimized the assay to find the concen- tration of MMS that gave the biggest difference between wild type S122 and S122A.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To counteract the adverse effects of various DNA lesions, cells have evolved an array of diverse repair pathways to restore DNA structure and to coordinate repair with cell cycle regulation. Chromatin changes are an integral part of the DNA damage response, particularly with regard to the types of repair that involve assembly of large multiprotein complexes such those involved in double strand break (DSB) repair and nucleotide excision repair (NER). A number of phosphorylation, acetylation, methylation, ubiquitylation and chromatin remodeling events modulate chromatin structure at the lesion site. These changes demarcate chromatin neighboring the lesion, afford accessibility and binding surfaces to repair factors and provide on-the-spot means to coordinate repair and damage signaling. Thus, the hierarchical assembly of repair factors at a double strand break is mostly due to their regulated interactions with posttranslational modifications of histones. A large number of chromatin remodelers are required at different stages of DSB repair and NER. Remodelers physically interact with proteins involved in repair processes, suggesting that chromatin remodeling is a requisite for repair factors to access the damaged site. Together, recent findings define the roles of histone post-translational modifications and chromatin remodeling in the DNA damage response and underscore possible differences in the requirements for these events in relation to the chromatin context.
    Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 10/2012; 752(1). DOI:10.1016/j.mrrev.2012.10.001 · 4.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Genetic recombination relies on a number of biochemical activities that must be present at the right time and place in order for two DNA molecules to be recombined properly. Recent advances in real-time fluorescence microscopy provide us with a glimpse of homologous recombination taking place in living cells. These approaches reveal that homologous recombination is highly choreographed in vivo with its spatio-temporal organization being dependent on both cell cycle phase and the nature of the initiating DNA lesion. In this chapter, we review the cell biology of homologous recombination in mitotic cells with the main focus on the yeast Saccharomyces cerevisiae but also drawing parallels to other eukaryotic organisms.