A novel strategy to identify proteins that interpret histone methylation patterns deposited by Set1 and Set2
Zusammenfassung der Projektergebnisse
Partitioning of eukaryotic chromosomes into euchromatic and heterochromatic domains is essential for gene regulation, chromosome segregation, and genome stability. Heterochromatin formation requires silencing factors, whereas the boundaries are thought to be shaped by anti‐silencing activities. We established a candidate knock‐out collection in S. pombe and screened this collection for factors implicated in heterochromatic gene silencing, by which we found 12 novel silencing factors. These factors include an uncharacterized ORF, for which we demonstrated an essential role in RNAi‐mediated silencing, Ers1. In addition, we identified the Cul4‐Ddb1Cdt2 complex, a conserved cullin‐based ubiquitin ligase, as a regulatory component in heterochromatin formation. In particular, we showed that Cul4‐Ddb1Cdt2 plays a key role in boundary formation. We demonstrate that it promotes poly‐ubiquitylation and degradation of the JmjC family member Epe1, an anti‐silencing protein that is paradoxically recruited to heterochromatin by HP1 silencing factors. Strikingly, Cul4‐Ddb1Cdt2 limits the spread of Epe1 into heterochromatic domains thereby restricting Epe1 accumulation to boundaries. Furthermore, genetic studies demonstrate that Epe1 restriction is necessary for region‐specific silencing and that Epe1 is the crucial target of Cul4. We conclude that ubiquitin‐dependent sculpting of the chromosomal distribution of an anti‐silencing factor is required for heterochromatin boundaries to form correctly.
Projektbezogene Publikationen (Auswahl)
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(2008). A comprehensive strategy enabling high‐resolution functional analysis of the yeast genome. Nat Methods. 5(8):711‐8
Breslow DK, Cameron DM, Collins SR, Schuldiner M, Stewart‐Ornstein J, Newman HW, Braun S, Madhani HD, Krogan NJ, Weissman JS
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(2008). Ers1, a rapidly diverging protein essential for RNA interference‐dependent heterochromatic silencing in Schizosaccharomyces pombe. J Biol Chem. 283(38):25770‐3
Rougemaille M, Shankar S, Braun S, Rowley M, Madhani HD
