M1 RNA is the RNA component of E. coli RNase P, one of tRNA-processing enzymes. The 3' flanking region of the rnpB gene coding for M1 RNA contains a 113 bp repeated sequence, successively reiterating 3.5 times, each of which includes the region for termination and the rne-dependent pentanucleotide sequence. Most transcription is terminated at the first terminator (T1), but complete termination requires the second terminator (T2) and the third (T3). Previous in vivo study has shown that deletion of the sequence between positions +331 and +383 almost abolished the termination efficiency at T1. This implies that the sequence from positions +331 to +383, which is preceding sequence to the termination hairpin, has a sequence required for efficient termination at T1. To determine this sequence, the sequence was sequentially deleted from positions +331 to +383. As more bases were deleted, run-through transcripts over T1 increased gradually. Especially the sequence between +364 and +373 was important because the termination efficiency apparently decreased with the deletion of this sequence. E. coli rnets strain was also used to exclude the possible involvement of RNA processing in determining the in vivo T1 termination efficiency. Mutagenesis experiments were carried out to examine specific sequence-requirement for efficient termination. The sequences between positions +364 and +373, GGUCAGUUUC, is important for the efficient T1 termination. In vivo transcription termination efficiencies were higher than in vitro, suggesting that the transcription of the rnpB gene be terminated in a factor-dependent fashion as well as by intrinsic terminator.
M1 RNA는 tRNA의 5' 말단을 성숙시키는 대장균 RNase P의 RNA 성분으로, rnpB 유전자로부터 암호화된다. rnpB 유전자의 3'인접 영역에 존재하는 반복 염기 서열들이 전사종결과정에 어떤 기능을 담당하는가를 조사하였다. 이 3' 인접영역은 113 bp의 염기서열이 약 3.5회 반복되며, 첫번째 종결유전자(T1), 두번째 종결유전자(T2), 세번째 종결유전자(T3)가 존재함으로 전사종결반을을 진행시킨다. 그 중 첫번째 종결유전자 (T1)에서 대부분의 종결과정이 이루어진다. 첫번째 종결유전자(T1)의 전사종결과정의 필수요인을 알아보기 위하여, 첫번째 반복단위에 해당하는 염기서열의 결실실험과 돌연변이화 실험을 생체내와 시험관내에서 수행하였다. 그 결과, +364번째 염기로부터 +373 번째 염기까지의 10개의 뉴클레오타이드(GGUCAGUUUC)가 중요한 의미를 지님을 알았다. 그리고 rnpB 유전자에 의한 전사 종결반응은 종결유전자만으로도 이루어지지만, 여러 다른 인자들의 도움에 의해 더 효율적으로 이루어짐을 볼 수 있었다.
