파아지 SP6 RNA 중합효소의 전사 개시위치 선정에 대한 돌연변이적 분석

Abstract

The transcription initiation sites of the mutants containing various sequences around the initiation site of phage SP6 promoter were determined. Precise sizing of the abortive elongation product RNAs from the nucleotide-specific pausings of the phage SP6 RNA polymerase under nucleotide-limiting conditions determined the initiation site of each mutant. When the wild-type +1 G is changed to C or A without change in the upstream sequence including TATA from -4 to -1, it still starts only at the + 1 site. Therefore, it seems that the phage SP6 RNA polymerase selects the initiation site precisely at a certain distance from a direct contact point in the upstream promoter sequence, regardless of the species of initiating nucleotide. But, the mutant containing TATCC from -4 to + 1 starts transcription at both positions -1 C and + 1 C. This shift of the initiation site seems to be caused by the sequence-dependent perturbations of DNA helical structure, D form to B form.