Bent DNA at a yeast autonomously replicating sequence

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Abstract
DNA fragments that show retarded electrophoretic mobility through poly aery lamide gels have been found in both prokaryotes and eukaryotes1–7. In the case of kinetoplast DNA, evidence has been presented that the DNA is curved or ‘bent’8,9. Bent DNA has previously been found at the λ and simian virus 40 (SV40) DNA replication origins6,7. Here we show the existence of bent DNA at a yeast autonomously replicating sequence (ARS1), a putative replication origin. The bent DNA has been localized to a 40–55 base pair (bp) segment and contains six (A)3–5 stretches (that is, six poly(A) stretches, three to five nucleotides in length) phased approximately every 10.5 bp. This region contains a DNA binding site for a yeast protein factor. This site lies at the 3′ end of the TRP1 gene, in a region devoid of nucleosomes, and is positioned 80 bp away from the ARS consensus sequence; removal of this region impairs ARS function in vivo. The bent DNA may be involved in transcription termination or the prevention of nucleosome assembly in this region.