Ribosomal RNA operon anti-termination. Function of leader and spacer region box B-box A sequences and their conservation in diverse micro-organisms.
All Escherichia coli rrn operons show a common motif in which anti-terminator box B-box A sequences occur twice, first in the leader and again in the 16 S-23 S spacer. In this study we have analyzed several aspects of rrn anti-termination by leader and spacer anti-terminator sequences. Using DNA synthesis and a plasmid test system, we incorporated random changes into the leader anti-terminator region and examined these mutations for their ability to read through a strong terminator. We also examined anti-termination by synthetic box A and by rrn spacer region sequences. Information derived from these experiments was used to search the rrn sequences of other micro-organisms for possible anti-termination features. Our principal conclusions were that: (1) box A was sufficient for terminator readthrough; (2) we could show no positive requirement for box B in our test system; (3) many of the negative anti-terminator mutations caused a promoter up-effect in the absence of a terminator; (4) the search of rrn operons from other micro-organisms revealed that anti-terminator-like box B-box A sequences exist in leader and spacer regions of both eubacteria and archaebacteria. The frequent occurrence of this pattern suggested that the E. coli rrn anti-termination motif is widespread in nature and has been conserved in microbial evolution.
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Department of Biological Sciences, Columbia University, New York, NY 10027.
Squires
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D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D004926:Escherichia coli; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D012329:RNA, Bacterial / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics*; D015183:Restriction Mapping; D013728:Terminator Regions, Genetic
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012335:RNA, Ribosomal