Xenopus TFIIIA Gene Transcription Is Dependent on cis-Element Positioning and Chromatin Structure

ABSTRACT

The Xenopus TFIIIA gene is transcribed very efficiently in oocytes. In addition to a TATA element at −30, we show that from −425 to +7 the TFIIIA gene contains only two positive ciselements centered at −267 (element 1) and −230 (element 2). This arrangement of the cis elements in the TFIIIA gene is striking because these two elements are positioned very close to each other yet separated from the TATA element by approximately 190 nucleotides. We show that the 190-nucleotide spacing between the TATA element and the upstream cis elements (elements 1 and 2) is critical for efficient transcription of the gene in oocytes and that a nucleosome is positioned in this intervening region. This nucleosome may act positively on TFIIIA transcription in oocytes by placing transcription factors bound at elements 1 and 2 in a favorable position relative to the transcription complex at the TATA element.

ACKNOWLEDGMENTS

We thank Alan Wolffe, Harry Jarrett, Roland Stein, and Tony Weil for reviewing the manuscript and for their many helpful suggestions during the course of this study.

This work was supported by NIH grant GM 39234 to W.L.T.