Abstract
Transcription of vertebrate U6 snRNA genes by RNA polymerase III requires two sequence elements in the proximal promoter region: the PSE (proximal sequence element, found in snRNA promoters transcribed by RNA polymerase II) and the TATA element (found in many mRNA promoters). The locations of the PSE and the TATA box are important determinants for transcriptional start site selection in their respective RNA polymerase II promoters. In vertebrate U6 genes the PSE and the TATA elements are located in approximately the same positions as in the polymerase II transcribed genes. However, their respective roles in initiation site selection, transcriptional efficiency and polymerase specificity are not known. I have analyzed the effects of spacing changes between the PSE and the TATA element, and between the two elements and the normal U6 start site on human U6 gene transcription in vitro and in transfected cells. My results discount the possibility that the location of either the PSE or the TATA element, by itself, dictates efficient selection of a transcriptional start site. Instead, I suggest that the two elements form a compound promoter element whose location dictates the start site of transcription from the hum an U6 gene promoter. Spacing changes between the PSE and the TATA element result in greatly reduced levels of transcription. These observations suggest the possibility that the factors that bind these two elements interact with each other. To test this hypothesis, I further investigated the possible interaction of the PSE and TATA binding proteins (PBP and TBP) when bound to normal or mutant U6 proximal promoters using a gel mobility shift assay. I detect a complex containing both PBP and TBP bound to the wild-type U6 promoter. Efficient formation of the triple complex is dependent on the presence of the PSE and the TATA box on the template DNA. Furthermore, U6 mutant promoters containing an increased spacing between the PSE and TATA box of 5 or 10 bp are impaired in the ability to form a complex that includes TBP. I infer from these results that PBP and TBP interact when their binding sites are properly positioned in a U6 gene promoter.
Goomer, Randal S. (1993). Characterization of the role of the proximal sequence element (PSE) and the TATA box in the human U6 small nuclear RNA (snRNA) gene transcription. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1526946.