title: The Saccharomyces cerevisiae histone chaperone Rtt106 mediates the cell cycle recruitment of SWI/SNF and RSC to the HIR-dependent histone genes.
abstract: BACKGROUND
  In Saccharomyces cerevisiae, three out of the four histone gene pairs (HTA1-HTB1, HHT1-HHF1, and HHT2-HHF2) are regulated by the HIR co-repressor complex. The histone chaperone Rtt106 has recently been shown to be present at these histone gene loci throughout the cell cycle in a HIR- and Asf1-dependent manner and involved in their transcriptional repression. The SWI/SNF and RSC chromatin remodeling complexes are both recruited to the HIR-dependent histone genes; SWI/SNF is required for their activation in S phase, whereas RSC is implicated in their repression outside of S phase. Even though their presence at the histone genes is dependent on the HIR complex, their specific recruitment has not been well characterized. In this study we focused on characterizing the role played by the histone chaperone Rtt106 in the cell cycle-dependent recruitment of SWI/SNF and RSC complexes to the histone genes.
  
  
  RESULTS
  Using GST pull-down and co-immunoprecipitation assays, we showed that Rtt106 physically interacts with both the SWI/SNF and RSC complexes in vitro and in vivo. We then investigated the function of this interaction with respect to the recruitment of these complexes to HIR-dependent histone genes. Using chromatin immunoprecipitation assays (ChIP), we found that Rtt106 is important for the recruitment of both SWI/SNF and RSC complexes to the HIR-dependent histone genes. Furthermore, using synchronized cell cultures, we showed by ChIP assays that the Rtt106-dependent SWI/SNF recruitment to these histone gene loci is cell cycle regulated and restricted to late G1 phase just before the peak of histone gene expression in S phase.
  
  
  CONCLUSIONS
  Overall, these data strongly suggest that the interaction between the histone chaperone Rtt106 and both the SWI/SNF and RSC chromatin remodeling complexes is important for the cell cycle regulated recruitment of these two complexes to the HIR-dependent histone genes.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Monica E
authors.initials: ME
authors.lastname: Ferreira
authors.forename: Kacie
authors.initials: K
authors.lastname: Flaherty
authors.forename: Philippe
authors.initials: P
authors.lastname: Prochasson
mesh_terms: D002453:Cell Cycle; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D047468:Immunoprecipitation; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D018832:Molecular Chaperones; C505157:Rtt106 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins