DNA-guided establishment of nucleosome patterns within coding regions of a eukaryotic genome
Abstract
A conserved hallmark of eukaryotic chromatin architecture is the distinctive array of well-positioned nucleosomes downstream from transcription start sites (TSS). Recent studies indicate that trans-acting factors establish this stereotypical array. Here, we present the first genome-wide in vitro and in vivo nucleosome maps for the ciliate Tetrahymena thermophila. In contrast with previous studies in yeast, we find that the stereotypical nucleosome array is preserved in the in vitro reconstituted map, which is governed only by the DNA sequence preferences of nucleosomes. Remarkably, this average in vitro pattern arises from the presence of subsets of nucleosomes, rather than the whole array, in individual Tetrahymena genes. Variation in GC content contributes to the positioning of these sequence-directed nucleosomes and affects codon usage and amino acid composition in genes. Given that the AT-rich Tetrahymena genome is intrinsically unfavorable for nucleosome formation, we propose that these "seed" nucleosomes--together with trans-acting factors--may facilitate the establishment of nucleosome arrays within genes in vivo, while minimizing changes to the underlying coding sequences.
Associated Datasets
References
Evidence for purifying selection against synonymous mutations in mammalian exonic splicing enhancers
Citations
Nucleosomal signatures impose nucleosome positioning in coding and noncoding sequences in the genome
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CZI Human Cell Atlas Seed Network
The aim of the Human Cell Atlas (HCA) is to build reference maps of all human cells in order to enhance our understanding of health and disease. The Seed Networks for the HCA project aims to bring together collaborators with different areas of expertise in order to facilitate the development of the HCA. Find the latest research from members of the HCA Seed Networks here.