Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents

This Article PDF (Full Text) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Wells, W. A. Search for Related Content PubMed Articles by Wells, W. A. Social Bookmarking                      What's this?

A chromatin-remodeling complex binds actin filament ends and junctions. Crabtree/NAS

Crabtree's study of antigen-stimulated lymphocyte activation has previously shown that phosphatidylinositol 4,5-bisphosphate (PIP₂) signaling helps retain a greater proportion of a mammalian chromatin remodeling complex called BAF in the nucleus. Rando and Crabtree have now determined that BAF binds PIP₂ directly, but only if the complex retains two particular subunits: actin and the actin-related protein BAF53.

PIP₂ does not trigger exchange of BAF's actin subunit, but PIP₂ plus BAF does increase the extent of in vitro actin polymerization. In vitro, BAF binds PIP₂ vesicles and the ends and junctions of actin filaments.

Crabtree found that actin contacted two separate domains of the Brg1 subunit of BAF, but only one of these contacts was regulated by PIP₂. He suggests that PIP₂ may free up a domain of actin so that it can interact with other actin subunits, thus anchoring the complex in the nucleus.

The interaction is unlikely to involve long actin polymers. These have not been seen in the nucleus, despite extensive searches. Instead, Crabtree suggests that BAF might interact with a short actin polymer, immediately capped off, that then binds to a membranous structure. "It's a speculative model," he says, "but it's consistent with all the data we have at the moment."

Crabtree is not the only one interested in inositol derivatives. Carl Wu (NIH, Bethesda, MD) and Erin O'Shea (University of California, San Francisco, CA) have recently found in vitro and in vivo evidence for regulation of chromatin remodeling by certain water-soluble inositol polyphosphates. The connection with Crabtree's work remains unclear, however, as the inositol polyphosphates directly regulate remodeling activity, rather than affecting nuclear tethering or a nuclear matrix.

Reference:

Rando, O.J., et al. 2002. Proc. Natl. Acad. Sci. USA. 99:2824–2829.[Abstract/Free Full Text]

William A. Wells

wellsw{at}rockefeller.edu

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This Article PDF (Full Text) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Wells, W. A. Search for Related Content PubMed Articles by Wells, W. A. Social Bookmarking                      What's this?