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Destabilization of nucleosomes by an unusual DNA conformation adopted by poly(dA)·poly(dT) tracts in vivo
Author(s) -
Shimizu Mitsuhiro,
Mori Tatsuhiro,
Sakurai Takayuki,
Shindo Heisaburo
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.13.3358
Subject(s) - biology , nucleosome , dna , in vivo , genetics , microbiology and biotechnology , biophysics , histone , evolutionary biology
Poly(dA)·poly(dT) tracts are common and often found upstream of genes in eukaryotes. It has been suggested that poly(dA)·poly(dT) promotes transcription in vivo by affecting nucleosome formation. On the other hand, in vitro studies show that poly(dA)·poly(dT) can be easily incorporated into nucleosomes. Therefore, the roles of these tracts in nucleosome organization in vivo remain to be established. We have developed an assay system that can evaluate nucleosome formation in yeast cells, and demonstrated that relatively longer tracts such as A 15 TATA 16 and A 34 disrupt an array of positioned nucleosomes, whereas a shorter A 5 TATA 4 tract is incorporated in positioned nucleosomes of yeast minichromosomes. Thus, nucleosomes are destabilized by poly(dA)·poly(dT) in vivo in a length‐dependent manner. Furthermore, in vivo UV footprinting revealed that the longer tracts adopt an unusual DNA structure in yeast cells that corresponds to the B ′ conformation described in vitro . Our results support a mechanism in which a unique poly(dA)· poly(dT) conformation presets chromatin structure to which transcription factors are accessible.