SWR1 Complex Poises Heterochromatin Boundaries for Antisilencing Activity Propagation

Abstract

In eukaryotes, chromosomal processes are usually modulated through chromatin-modifying complexes that are dynamically targeted to specific regions of chromatin. In this study, we show that the chromatin-remodeling complex SWR1 (SWR1-C) uses a distinct strategy to regulate heterochromatin spreading. Swr1 binds in a stable manner near heterochromatin to prepare specific chromosomal regions for H2A.Z deposition, which can be triggered by NuA4-mediated acetylation of histone H4. We also demonstrate through experiments with Swc4, a module shared by NuA4 and SWR1-C, that the coupled actions of NuA4 and SWR1-C lead to the efficient incorporation of H2A.Z into chromatin and thereby synergize heterochromatin boundary activity. Our results support a model where SWR1-C resides at the heterochromatin boundary to maintain and amplify antisilencing activity of histone H4 acetylation through incorporating H2A.Z into chromatin.

Supplemental material for this article may be found at http://mcb.asm.org/.

We thank Brian A. Lenzmeier (Buena Vista University, Storm Lake, IA) for his critical reading of our manuscript. We thank Susan M. Gasser, who generously provided the plasmids for the lacO targeting system.

This project was supported by grants from the Ministry of Science and Technology of China (2005CB522402) and the National Natural Science Foundation of China (90919027).

We declare that no competing interests exist.