RNA 97 (the RNA Society), May 27 - June 1 1996, Banff, Canada

Evolutionary variation in RNase P RNA structure in Bacteria and Archaea.

James W. Brown, Elizabeth S. Haas, Beverly M. Vucson, James A. Pannucci, and J. Kirk Harris. North Carolina State University Raleigh, NC 27695

RNase P is the endoribonuclease responsible for 5' maturation of tRNA precursors. In all organisms and organelles that synthesis tRNA (except possibly the chloroplasts of green plants), RNase P is a ribonucleoprotein. We have used comparative methods to survey and analyze the structure of the RNA components of the RNase P enzymes of Bacteria and Archaea. Genes encoding RNase P RNA have been cloned and analyzed from each of the major evolutionary branches from both groups; 138 bacterial and 28 archaeal sequences are now available for analysis. All of the bacterial RNAs tested so far, including those of the Planctomycetes, Chlamydiae, and green non-sulfur Bacteria, are catalytically-proficient by themselves in vitro. Although the RNase P RNAs in Archaea closely resemble the bacterial RNAs in sequence and secondary structure, they are not catalytically active in vitro. There are two clear instances of structural convergence in this survey: the overall structures of the RNAs from the low G+C Gram-positive Bacteria and green non-sulfur Bacteria (esp. Thermomicrobium), and the P15/16 region of the Chlamydiae and Crenarchaea. The variation in sequence and structure motif alternatives in both groups will be described. Phylogenetic trees based on RNase P RNA sequences are indistinguishable in branching order from those based on small-subunit ribosomal RNAs.