SCHIZOSACCHAROMYCES-POMBE RNASE MRP RNA IS HOMOLOGOUS TO METAZOAN RNASE MRP RNAS AND MAY PROVIDE CLUES TO INTERRELATIONSHIPS BETWEEN RNASE-MRP AND RNASE-P
Jl. Paluh et Da. Clayton, SCHIZOSACCHAROMYCES-POMBE RNASE MRP RNA IS HOMOLOGOUS TO METAZOAN RNASE MRP RNAS AND MAY PROVIDE CLUES TO INTERRELATIONSHIPS BETWEEN RNASE-MRP AND RNASE-P, Yeast, 11(13), 1995, pp. 1249-1264
RNase MRP and RNase P ribonucleoproteins are structurally and function
ally similar across a large evolutionary distance. To better character
ize possible complex interrelationships between these two enzymes, we
have employed the fission yeast Schizosaccharomyces pombe. Unlike Sacc
haromyces cerevisiae, S. pombe is believed to harbour only one genetic
locus for the RNA component of RNase P and does not contain a known m
itochondrially encoded RNase P RNA. We have identified the single nucl
ear gene for the RNA component of RNase MRP in S. pombe, mrp-l, by hom
ology to vertebrate RNase MRP RNAs. The mrp-l gene encodes an RNA of m
aximum mature length 400 nucleotides that shares a high degree of iden
tity, in evolutionarily conserved regions, to both vertebrate RNase MR
P RNAs and S. pombe RNase P RNA. Disruption of mrp-l in the diploid st
rain SP826 and sporulation of tetrads resulted in a 2 dead:2 viable se
gregation, consistent with the gene being essential. Lethality is resc
ued by a plasmid-borne copy of mrp-l. Partially purified ribonucleopro
tein RNase MRP activity correctly and efficiently processed all previo
usly characterized heterologous mitochondrial RNA substrates. The comp
act mitochondrial genome of S. pombe contains sequence elements with >
50% identity to mammalian D-loop CSBI and CSBII elements. The identifi
cation of mrp-l in S. pombe should facilitate not only comparisons bet
ween the related ribonucleoproteins RNase MRP and RNase P, but should
also provide an opportunity for genetic elucidation of RNase MRP funct
ion in a situation reflective of the animal kingdom.