RT Journal
A1 Andersson, Robin
A1 Enroth, Stefan
A1 Rada-Iglesias, Alvaro
A1 Wadelius, Claes
A1 Komorowski, Jan
T1 Nucleosomes are well positioned in exons and carry characteristic histone modifications
JF Genome Research 
JO Genome Research 
YR 2009 
FD October 01 
VO 19 
IS 10 
SP 1732 
OP 1741 
DO 10.1101/gr.092353.109 
UL http://genome.cshlp.org/content/19/10/1732.abstract 
AB The genomes of higher organisms are packaged in nucleosomes with functional histone modifications. Until now, genome-wide nucleosome and histone modification studies have focused on transcription start sites (TSSs) where nucleosomes in RNA polymerase II (RNAPII) occupied genes are well positioned and have histone modifications that are characteristic of expression status. Using 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. Among the 38 histone modifications analyzed in man, H3K36me3, H3K79me1, H2BK5me1, H3K27me1, H3K27me2, and H3K27me3 had evidently higher signals in internal exons than in the following introns and were clearly related to exon expression. These observations are suggestive of roles in splicing. Thus, exons are not only characterized by their coding capacity, but also by their nucleosome organization, which seems evolutionarily conserved since it is present in both primates and nematodes.