Unusual combinatorial involvement of poly-A/T tracts in organizing genes and chromatin in Dictyostelium.
Genome Res
; 22(6): 1098-106, 2012 Jun.
Article
em En
| MEDLINE
| ID: mdl-22434426
ABSTRACT
Dictyostelium discoideum is an amoebozoa that exists in both a free-living unicellular and a multicellular form. It is situated in a deep branch in the evolutionary tree and is particularly noteworthy in having a very A/T-rich genome. Dictyostelium provides an ideal system to examine the extreme to which nucleotide bias may be employed in organizing promoters, genes, and nucleosomes across a genome. We find that Dictyostelium genes are demarcated precisely at their 5' ends by poly-T tracts and precisely at their 3' ends by poly-A tracts. These tracts are also associated with nucleosome-free regions and are embedded with precisely positioned TATA boxes. Homo- and heteropolymeric tracts of A and T demarcate nucleosome border regions. Together, these findings reveal the presence of a variety of functionally distinct polymeric A/T elements. Strikingly, Dictyostelium chromatin may be organized in di-nucleosome units but is otherwise organized as in animals. This includes a +1 nucleosome in a position that predicts the presence of a paused RNA polymerase II. Indeed, we find a strong phylogenetic relationship between the presence of the NELF pausing factor and positioning of the +1 nucleosome. Pausing and +1 nucleosome positioning may have coevolved in animals.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Poli A
/
Poli T
/
Cromatina
/
Nucleossomos
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Dictyostelium
Limite:
Animals
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article