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.
We thank Marc Lavigne and Robert Kingston for providing labeled nucleosome arrays for chromatin remodeling assays and Carolyn Slayman for YCp2HSE. We thank Steve Buratowski for advice on ChIP and for providing the polyclonal α-TBP antibody. We thank Christophe Briand for assistance with the interpretation of dynamic light scattering results. This work was supported by the Swiss National Science Foundation (SNF) grant # 823A-061192 to Z.O.J. and American Cancer Society (ACS) grant # RSG-01-055–01-CCG to A.D.