Rvb1p/Rvb2p Recruit Arp5p and Assemble a Functional Ino80 Chromatin Remodeling Complex

Abstract

The Rvb1p and Rvb2p (or TIP48 and TIP49) nuclear ATP binding proteins are universally conserved in eukaryotes and essential for viability of yeasts. Rvbp associate with each other as a double hexamer, with YHR034c and with two complexes involved in chromatin remodeling, Ino80.com and Swr1.com. Loss of Rvb1p or Ino80p affects many yeast promoters similarly. Rvbp are not essential for the recruitment of Ino80p to promoters but are essential for the catalytic activity of Ino80.com. Loss of Rvbp leads to loss of the functionally critical Arp5p in Ino80.com. Rvb2p associates with Arp5p in vitro in a reaction dependent on the presence of ATP and Ino80p. Therefore, Rvbp are required for the structural and functional integrity of the Ino80 chromatin remodeling complex.

INO80 subfamily of chromatin remodeling complexes

“…Several other global gene expression profiling experiments also showed that the INO80 complex regulates a specific set of gene both negatively and positively [9,47]. Two phosphate regulated genes, PHO5 and PHO84 were used to study the promoter regulation mechanism of INO80, and it was found that INO80 had a repressive effect on the PHO5 promoter and a stimulatory effect on the PHO84 promoter, suggesting that INO80 is required for proper regulation of these promoters [17]. Furthermore, in vitro transcription assays show a 10 fold increase in transcriptional activation of chromatin remodeled by INO80.com [8].…”

“…It has been shown that ino80 null mutants exhibited decreased gene activation mediated by a UAS element, ICRE (inositol/choline-responsive element), and pleiotropic expression defects [12]. In a microarray assay, it was found that 150 out of 5602 yeast genes showed at least 2 fold change in mRNA level upon acute removal of INO80, with roughly equal numbers of up regulated and down regulated genes [17]. Several other global gene expression profiling experiments also showed that the INO80 complex regulates a specific set of gene both negatively and positively [9,47].…”

“…They further found that loss of Rvb proteins leads to the loss of Arp5, a functionally important subunit of INO80.com [10]. Their in vitro studies reveal that Rvbs and Arp5 associate in a complex and the interaction is Ino80 and ATP dependent [17]. Moreover, a recent proteomic study showed that Arp5 and Rvb1 can associate with each other and form a module [21].…”

“…Recently, it was shown by the Dutta group that Rvb proteins are essential for the chromatin remodeling activity of INO80.com [17]. They further found that loss of Rvb proteins leads to the loss of Arp5, a functionally important subunit of INO80.com [10].…”

“…It is worth noting that Rvbs are subunits of the Swr1 complex as well, which does not contain Arp5, suggesting that one of the Swr1 subunits (such as Arp6) or another unknown polypeptide may associate with Rvbs and be required for the regulation of SWR1.com. Although it has been found that Sec53 (a phosphomannomutase) and Rvb2 can form a module in vivo [21], and that Pih1 (protein of unresolved function) associates with Rvb1 and Rvb2 to form a light Rvb.com [17], none of them has been related to chromatin remodeling functions.…”