期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1986
卷号：83
期号：11
页码：3614-3618
DOI：10.1073/pnas.83.11.3614
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Promoters for T7 RNA polymerase have a highly conserved sequence of 23 continuous base pairs located at position -17 to +6 relative to the initiation site for the RNA. The complex of T7 RNA polymerase with the phage phi 10 promoter has been visualized indirectly by exploiting the ability of the polymerase to protect DNA sequences from cleavage by methidiumpropyl-EDTA X Fe(II). The DNA contacts made by T7 RNA polymerase have been mapped during binding and during the subsequent initiation of transcription. The RNA polymerase alone protects 19 bases in a region from -21 to -3. Synthesis of the trinucleotide r(GGG) expands the length of the sequence protected by the RNA polymerase and stabilizes the complex; 29 bases (-21 to +8) are protected, and the observed equilibrium association constant of the r(GGG) complex is 5 X 10(5) M-1. The formation of a hexanucleotide mRNA, r(GGGAGA), further extends the protected region; 32 bases (-21 to +11) are protected. Finally, the synthesis of a pentadecanucleotide mRNA leads to a translocation of the region protected by the protein; the sequence now protected is reduced to 24 bases (-4 to +20).
