What is the relationship between nucleosomes and exons?
['Nucleosomes preferentially are located at the ends of exons, thus protecting splice junctions, with the N9 positions of guanines of the GT and AG junctions oriented toward the histones.', 'Nucleosomes were found to be preferentially positioned within constitutive exons and/or constitutive portions of alternative exons, which was not associated with gene expression or states of cells but was based on sequence and positively related with the sequence conservation of splicing sites', 'Here, we discuss the evidence supporting these ideas, from the first proposal of chromatin affecting alternative splicing, performed 20 years ago, to the latest findings including genome-wide evidence that nucleosomes are preferentially positioned in exons.', 'Here we show, by analysis of data sets from human sperm and T cells and medaka (Japanese killifish, Oryzias latipes) blastulae, that internal exons of genes are characterized by sharply elevated average nucleosome occupancy in comparison to flanking intronic sequences.', 'sing public data, we here show that there is a higher nucleosome-positioning signal in internal human exons and that this positioning is independent of expression. We observed a similarly strong nucleosome-positioning signal in internal exons of Caenorhabditis elegans.', 'we have found stable nucleosome occupancy within human and Caenorhabditis elegans exons that is stronger in exons with weak splice sites.', 'This confirms previously reported findings about preferential positioning of splice junctions within the nucleosomes.']
['Nucleosomes are preferentially located within exons compared to nearby intronic sequences. Preferential positioning within the exons is indepedent of gene expression levels, stronger in exons with weak splice sites and conserved through metazoan evolution.']
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