Yin and Yang of Histone H2B Roles in Silencing and Longevity: A Tale of Two Arginines.
Summary of "Yin and Yang of Histone H2B Roles in Silencing and Longevity: A Tale of Two Arginines."
In budding yeast, silent chromatin is defined at the region of telomeres, rDNA loci and silent mating loci. Although the silent chromatin at different loci shows structural similarity, the underlying mechanism to establish, maintain and inherit these structures may be fundamentally different. In this study, we found two arginine residues within histone H2B, which are specifically required to maintain either the telomeric or the rDNA silenct chromatin. Arginine 95 (R95) plays a specific role at telomeres whereas Arginine 102 (R102) is required to maintain the silent chromatin at rDNA and to ensure the integrity of rDNA loci by suppressing recombination between rDNA repeats. R95 mutants show enhanced rDNA silencing but a paradoxically low Sir2 protein abundance. Furthermore weakened silencing at telomeres in R95 mutants can be suppressed by a specific SIR3 allele, SIR3-D205N, which increases the affinity of Sir proteins to telomeres, suggesting H2B-R95 may directly mediate telomeric Sir protein-nucleosome interactions. Double mutations of R95 and R102 lead to desilencing of both rDNA and telomeres, indicating both arginines are necessary to ensure integrity of silent chromatin at these loci. Furthermore, mutations of R102 cause accumulation of extrachromosomal rDNA circles and reduce lifespan, suggesting that histone H2B contributes to longevity.
Affiliation
Johns Hopkins University School of Medicine.
Journal Details
This article was published in the following journal.
Name: Genetics
ISSN: 1943-2631
Pages:
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/20713692
- DOI: http://dx.doi.org/10.1534/genetics.110.118489
Medical and Biotech [MESH] Definitions
Nucleoplasmins
A family of histone molecular chaperones that play roles in sperm CHROMATIN decondensation and CHROMATIN ASSEMBLY in fertilized eggs. They were originally discovered in XENOPUS egg extracts as histone-binding factors that mediate nucleosome formation in vitro.
Yang Deficiency
In the YIN-YANG system of philosophy and medicine, a lack of vital energy (called yangxu in Chinese). It manifests itself in various systemic and organic diseases. (The Pinyin Chinese-English Dictionary, 1979)
Yin-yang
In Chinese philosophy and religion, two principles, one negative, dark, and feminine (yin) and one positive, bright, and masculine (yang), from whose interaction all things are produced and all things are dissolved. As a concept the two polar elements referred originally to the shady and sunny sides of a valley or a hill but it developed into the relationship of any contrasting pair: those specified above (female-male, etc.) as well as cold-hot, wet-dry, weak-strong, etc. It is not a distinct system of thought by itself but permeates Chinese life and thought. A balance of yin and yang is essential to health. A deficiency of either principle can manifest as disease. (Encyclopedia Americana)
Histone Deacetylase 1
A histone deacetylase subtype that is found along with HISTONE DEACETYLASE 2; RETINOBLASTOMA-BINDING PROTEIN 4; and RETINOBLASTOMA-BINDING PROTEIN 7 as core components of histone deacetylase complexes.
Histone Deacetylase 2
A histone deacetylase subtype that is found along with HISTONE DEACETYLASE 1; RETINOBLASTOMA-BINDING PROTEIN 4; and RETINOBLASTOMA-BINDING PROTEIN 7 as core components of histone deacetylase complexes.
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