Histone H3 lysine 4 methylation is mediated by Set1 and promotes maintenance of active chromatin states in fission yeast.
Methylation of histone H3 at lysine 4 (H3 Lys-4) or lysine 9 (H3 Lys-9) is known to define active and silent chromosomal domains respectively from fission yeast to humans. However, in budding yeast, H3 Lys-4 methylation is also necessary for silent chromatin assembly at telomeres and ribosomal DNA. Here we demonstrate that deletion of set1, which encodes a protein containing an RNA recognition motif at its amino terminus and a SET domain at the carboxy terminus, abolishes H3 Lys-4 methylation in fission yeast. Unlike in budding yeast, Set1-mediated H3 Lys-4 methylation is not required for heterochromatin assembly at the silent mating-type region and centromeres in fission yeast. Our analysis suggests that H3 Lys-4 methylation is a stable histone modification present throughout the cell cycle, including mitosis. The loss of H3 Lys-4 methylation in set1Delta cells is correlated with a decrease in histone H3 acetylation levels, suggesting a mechanistic link between H3 Lys-4 methylation and acetylation of the H3 tail. We suggest that methylation of H3 Lys-4 primarily acts in the maintenance of transcriptionally poised euchromatic domains, and that this modification is dispensable for heterochromatin formation in fission yeast, which instead utilizes H3 Lys-9 methylation.
Noma
Ken-ichi
K
Cold Spring Harbor Laboratory, P.O. Box 100, NY 11724, USA.
Grewal
Shiv I S
SI
D002453:Cell Cycle; D002843:Chromatin / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism*; D008745:Methylation; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
D002843:Chromatin; D006657:Histones; D008239:Lysine