title: Different nucleosomal architectures at early and late replicating origins in Saccharomyces cerevisiae.
abstract: BACKGROUND
  Eukaryotic genomes are replicated during S phase according to a temporal program. Several determinants control the timing of origin firing, including the chromatin environment and epigenetic modifications. However, how chromatin structure influences the timing of the activation of specific origins is still poorly understood.
  
  
  RESULTS
  By performing high-resolution analysis of genome-wide nucleosome positioning we have identified different chromatin architectures at early and late replication origins. These different patterns are already established in G1 and are tightly correlated with the organization of adjacent transcription units. Moreover, specific early and late nucleosomal patterns are fixed robustly, even in rpd3 mutants in which histone acetylation and origin timing have been significantly altered. Nevertheless, higher histone acetylation levels correlate with the local modulation of chromatin structure, leading to increased origin accessibility. In addition, we conducted parallel analyses of replication and nucleosome dynamics that revealed that chromatin structure at origins is modulated during origin activation.
  
  
  CONCLUSIONS
  Our results show that early and late replication origins present distinctive nucleosomal configurations, which are preferentially associated to different genomic regions. Our data also reveal that origin structure is dynamic and can be locally modulated by histone deacetylation, as well as by origin activation. These data offer novel insight into the contribution of chromatin structure to origin selection and firing in budding yeast.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Soriano
authors.forename: Esther C
authors.initials: EC
authors.lastname: Morafraile
authors.forename: Enrique
authors.initials: E
authors.lastname: Vázquez
authors.forename: Francisco
authors.initials: F
authors.lastname: Antequera
authors.affiliation: Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas/ Universidad de Salamanca (CSIC/USAL), Campus Miguel de Unamuno, Salamanca 37007, Spain. monicas@usal.es.
authors.forename: Mónica
authors.initials: M
authors.lastname: Segurado
mesh_terms: D000107:Acetylation; D042002:Chromatin Assembly and Disassembly; D042522:DNA Replication Timing; D004271:DNA, Fungal / Q000235:genetics*; D006655:Histone Deacetylases / Q000235:genetics*; D006657:Histones / Q000378:metabolism; D009154:Mutation; D009707:Nucleosomes / Q000378:metabolism*; D018741:Replication Origin; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D004271:DNA, Fungal; D006657:Histones; D009707:Nucleosomes; D029701:Saccharomyces cerevisiae Proteins; C071665:RPD3 protein, S cerevisiae; D006655:Histone Deacetylases