title: Gene size differentially affects the binding of yeast transcription factor tau to two intragenic regions.
abstract: Yeast transcription factor tau (transcription factor IIIC) specifically interacts with tRNA genes, binding to both the A block and the B block elements of the internal promoter. To study the influence of A block-B block spacing, we analyzed the binding of purified tau protein to a series of internally deleted yeast tRNA(3Leu) genes with A and B blocks separated by 0 to 74 base pairs. Optimal binding occurred with genes having A block-B block distances of 30-60 base pairs; the relative helical orientation of the A and B blocks was unimportant. Results from DNase I "footprinting" and lambda exonuclease protection experiments were consistent with these findings and further revealed that changes in A block-B block distance primarily affect the ability of tau to interact with A block sequences; B block interactions are unaltered. When the A block-B block distance is 17 base pairs or less, tau interacts with a sequence located 15 base pairs upstream of the normal A block, and a new RNA initiation site is observed by in vitro transcription. We propose that the initial binding of tau to the B block activates transcription by enhancing its ability to bind at the A block, and that the A block interaction ultimately directs initiation by RNA polymerase III.
authors.affiliation: Department of Genetics, University of Washington, Seattle 98195.
authors.forename: R E
authors.initials: RE
authors.lastname: Baker
authors.forename: S
authors.initials: S
authors.lastname: Camier
authors.forename: A
authors.initials: A
authors.lastname: Sentenac
authors.forename: B D
authors.initials: BD
authors.lastname: Hall
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000502:physiology; D005092:Exonucleases; D011401:Promoter Regions, Genetic; D012345:RNA, Transfer, Amino Acid-Specific / Q000235:genetics*; D012356:RNA, Transfer, Leu / Q000235:genetics*; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D012345:RNA, Transfer, Amino Acid-Specific; D012356:RNA, Transfer, Leu; D014157:Transcription Factors; D005092:Exonucleases