Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 104, Issue 7, Pages 2229-2234Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0611447104
Keywords
chromatin remodeling; promoter; transcription; nucleosome positioning
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In this article, the effect of a d(CG) DNA dinucleotide repeat sequence on RNA polymerase 11 transcription is examined in yeast Saccharomyces cerevisiae. Our previous report shows that a d(CG), dinucleotide repeat sequence located proximally upstream of the TATA box enhances transcription from a minimal CYC1 promoter in a manner that depends on its surrounding negative supercoiling. Here, we demonstrate that the d(CG)9 repeat sequence stimulates gene activity by forming a Z-DNA secondary structure. Furthermore, the extent of transcriptional enhancement by Z-DNA is promoter-specific and determined by its separation distance relative to the TATA box. The stimulatory effect exerted by promoter proximal Z-DNA is not affected by helical phasing relative to the TATA box, suggesting that Z-DNA effects transcription without interacting with the general transcription machinery by loopingout the intervening DNA. A nucleosome-scanning assay reveals that the d(CG)9 repeat sequence in the Z conformation blocks nucleosome formation, and it is found in the linker DNA with two flanking nucleosomes. This result suggests that Z-DNA formation proximally upstream of a promoter is sufficient to demarcate the boundaries of its neighboring nucleosomes, which produces transcriptionally favorable locations for the TATA box near the nucleosomal DNA-entry site and at dyad positions on the nucleosome. These findings suggest that Z-DNA formation in chromatin is a part of the genomic code for nucleosome positioning in vivo.
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