title: Insights into distinct regulatory modes of nucleosome positioning.
abstract: BACKGROUND
  The nucleosome is the fundamental unit of eukaryotic genomes. Experimental evidence suggests that the genomic DNA sequence and a variety of protein factors contribute to nucleosome positioning in vivo. However, how nucleosome positioning is determined locally is still largely unknown.
  
  
  RESULTS
  We found that transcription factor binding sites (TFBSs) with particular nucleosomal contexts show a preference to reside on specific chromosomes. We identified four typical gene classes associated with distinct regulatory modes of nucleosome positioning, and further showed that they are distinguished by transcriptional regulation patterns. The first mode involves the cooperativity between chromatin remodeling and stable transcription factor (TF)-DNA binding that is linked to high intrinsic DNA binding affinities, evicting nucleosomes from favorable DNA sequences. The second is the DNA-encoded low nucleosome occupancy that is associated with high gene activity. The third is through chromatin remodeling and histone acetylation, sliding nucleosomes along DNA. This mode is linked to more cryptic sites for TF binding. The last consists of the nucleosome-enriched organization driven by other factors that overrides nucleosome sequence preferences. In addition, we showed that high polymerase II (Pol II) occupancy is associated with high nucleosome occupancy around the transcription start site (TSS).
  
  
  CONCLUSIONS
  We identified four different regulatory modes of nucleosome positioning and gave insights into mechanisms that specify promoter nucleosome location. We suggest two distinct modes of recruitment of Pol II, which are selectively employed by different genes.
authors.affiliation: Electronic Department, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Dai
authors.forename: Xianhua
authors.initials: X
authors.lastname: Dai
authors.forename: Qian
authors.initials: Q
authors.lastname: Xiang
authors.forename: Jihua
authors.initials: J
authors.lastname: Feng
authors.forename: Yangyang
authors.initials: Y
authors.lastname: Deng
authors.forename: Jiang
authors.initials: J
authors.lastname: Wang
mesh_terms: D001665:Binding Sites; D002875:Chromosomes; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D009707:Nucleosomes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D009707:Nucleosomes; D014157:Transcription Factors