Centromere silencing and function in fission yeast is governed by the amino terminus of histone H3.
BACKGROUND
Centromeric domains often consist of repetitive elements that are assembled in specialized chromatin, characterized by hypoacetylation of histones H3 and H4 and methylation of lysine 9 of histone H3 (K9-MeH3). Perturbation of this underacetylated state by transient treatment with histone deacetylase inhibitors leads to defective centromere function, correlating with delocalization of the heterochromatin protein Swi6/HP1. Likewise, deletion of the K9-MeH3 methyltransferase Clr4/Suvar39 causes defective chromosome segregation. Here, we create fission yeast strains retaining one histone H3 and H4 gene; the creation of these strains allows mutation of specific N-terminal tail residues and their role in centromeric silencing and chromosome stability to be investigated.


RESULTS
Reduction of H3/H4 gene dosage to one-third does not affect cell viability or heterochromatin formation. Mutation of lysines 9 or 14 or serine 10 within the amino terminus of histone H3 impairs centromere function, leading to defective chromosome segregation and Swi6 delocalization. Surprisingly, silent centromeric chromatin does not require the conserved lysine 8 and 16 residues of histone H4.


CONCLUSIONS
To date, mutation of conserved N-terminal residues in endogenous histone genes has only been performed in budding yeast, which lacks the Clr4/Suvar39 histone methyltransferase and Swi6/HP1. We demonstrate the importance of conserved residues within the histone H3 N terminus for the maintenance of centromeric heterochromatin in fission yeast. In sharp contrast, mutation of two conserved lysines within the histone H4 tail has no impact on the integrity of centromeric heterochromatin. Our data highlight the striking divergence between the histone tail requirements for the fission yeast and budding yeast silencing pathways.
Mellone
Barbara G
BG
Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, 6.34 Swann Building, The University of Edinburgh, Mayfield Road, EH9 3JR, Edinburgh, United Kingdom.
Ball
Leslie
L
Suka
Noriyuki
N
Grunstein
Michael R
MR
Partridge
Janet F
JF
Allshire
Robin C
RC
D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism*; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002455:Cell Division / Q000235:genetics; D002503:Centromere / Q000235:genetics / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D020090:Chromosome Segregation; D003433:Crosses, Genetic; D020868:Gene Silencing; D006570:Heterochromatin / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism; D009154:Mutation; D011233:Precipitin Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism
D000911:Antibodies, Monoclonal; D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D006657:Histones; D029702:Schizosaccharomyces pombe Proteins; C465958:Swi6 protein, S pombe; D000123:Acetyltransferases; D008239:Lysine