Fission yeast CENP-B homologs nucleate centromeric heterochromatin by promoting heterochromatin-specific histone tail modifications.
Heterochromatin is a functionally important chromosomal component, especially at centromeres. In fission yeast, conserved heterochromatin-specific modifications of the histone H3 tail, involving deacetylation of Lys 9 and Lys 14 and subsequent methylation of Lys 9, promote the recruitment of a heterochromatin protein, Swi6, a homolog of the Drosophila heterochromatin protein 1. However, the primary determinants of the positioning of heterochromatin are still unclear. The fission yeast proteins Abp1, Cbh1, and Cbh2 are homologs of the human protein CENP-B that bind to centromeric alpha-satellite DNA and associate with centromeric heterochromatin. We show that the CENP-B homologs are functionally redundant at centromeres, and that Abp1 binds specifically to centromeric heterochromatin. In the absence of Abp1 or Cbh1, the centromeric association of Swi6 is diminished, resulting in a decrease in silencing of the region. CENP-B-homolog double disruptants show a synergistic reduction of Swi6 at centromeric heterochromatin, indicating that the three proteins are functionally redundant in the recruitment of Swi6. Furthermore, using chromatin immunoprecipitation assays, we show that disruption of CENP-B homologs causes a decrease in heterochromatin-specific modifications of histone H3. These results indicate that the CENP-B homologs act as site-specific nucleation factors for the formation of centromeric heterochromatin by heterochromatin-specific modifications of histone tails.
Nakagawa
Hiromi
H
Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan.
Lee
Joon-Kyu
JK
Hurwitz
Jerard
J
Allshire
Robin C
RC
Nakayama
Jun-Ichi
J
Grewal
Shiv I S
SI
Tanaka
Katsunori
K
Murakami
Yota
Y
D001324:Autoantigens; D001665:Binding Sites; D002503:Centromere / Q000378:metabolism*; D051936:Centromere Protein B; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D008840:Microfilament Proteins; D016296:Mutagenesis; D016254:Mutagenesis, Insertional; D010641:Phenotype; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
C062612:ABP1 protein, S cerevisiae; D001324:Autoantigens; C427236:Cbh2 protein, S pombe; D051936:Centromere Protein B; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006570:Heterochromatin; D006657:Histones; D008840:Microfilament Proteins; C075111:SWI6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; C400810:ura4 protein, S pombe