Transcription initiation and nuclease-sensitive sites upstream of the epsilon-globin gene in K562 cells are related to poly (dA).poly (dT) sequences.

Previous studies have documented transcription initiation sites and nuclease hypersensitive sites upstream of the epsilon-globin canonical cap site in K562 cells. The upstream transcription initiation sites coincide with some of the nuclease hypersensitive sites. Comparison of the positions of the upstream transcription initiation and the nuclease hypersensitive sites with the nucleotide base order shows that these upstream sites fall significantly closer to poly (dA).poly (dT) tracts than can reasonably be accounted for by chance. It is concluded that these sites are related to the occurrence of poly (dA).poly (dT) tracts of at least five base pairs. Other studies have related some particular functional properties to poly (dA).poly (dT) tracts. Additionally, poly (dA).poly (dT) tracts have been shown to have unusual physical characteristics and to produce an intrinsic bending of the DNA molecules in which they are located. This study indicates that poly (dA).poly (dT) tracts can provide access to DNA for RNA polymerases and induce a DNA conformation recognized by DNase I or S1 nuclease.