Pop3p is essential for the activity of the RNase MRP and RNase P ribonucleoproteins in vivo.
RNase MRP is a ribonucleoprotein (RNP) particle which is involved in the processing of pre-rRNA at site A3 in internal transcribed spacer 1. Although RNase MRP has been analysed functionally, the structure and composition of the particle are not well characterized. A genetic screen for mutants which are synthetically lethal (sl) with a temperature-sensitive (ts) mutation in the RNA component of RNase MRP (rrp2-1) identified an essential gene, POP3, which encodes a basic protein of 22.6 kDa predicted molecular weight. Over-expression of Pop3p fully suppresses the ts growth phenotype of the rrp2-1 allele at 34 degrees C and gives partial suppression at 37 degrees C. Depletion of Pop3p in vivo results in a phenotype characteristic of the loss of RNase MRP activity; A3 cleavage is inhibited, leading to under-accumulation of the short form of the 5.8S rRNA (5.8S(S)) and formation of an aberrant 5.8S rRNA precursor which is 5'-extended to site A2. Pop3p depletion also inhibits pre-tRNA processing; tRNA primary transcripts accumulate, as well as spliced but 5'- and 3'-unprocessed pre-tRNAs. The Pop3p depletion phenotype resembles those previously described for mutations in components of RNase MRP and RNase P (rrp2-1, rpr1-1 and pop1-1). Immunoprecipitation of epitope-tagged Pop3p co-precipitates the RNA components of both RNase MRP and RNase P. Pop3p is, therefore, a common component of both RNPs and is required for their enzymatic functions in vivo. The ubiquitous RNase P RNP, which has a single protein component in Bacteria and Archaea, requires at least two protein subunits for its function in eukaryotic cells.
Dichtl
B
B
EMBL, Gene Expression Programme, Heidelberg, Germany.
Tollervey
D
D
D000483:Alleles; D002470:Cell Survival; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004722:Endoribonucleases / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016296:Mutagenesis; D010641:Phenotype; D012326:RNA Splicing; D012329:RNA, Bacterial / Q000378:metabolism*; D016337:RNA, Catalytic / Q000378:metabolism*; D012331:RNA, Fungal / Q000378:metabolism; D043262:Ribonuclease P; D012261:Ribonucleoproteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D013696:Temperature
D004271:DNA, Fungal; D012329:RNA, Bacterial; D016337:RNA, Catalytic; D012331:RNA, Fungal; D012261:Ribonucleoproteins; D004722:Endoribonucleases; C058330:mitochondrial RNA-processing endoribonuclease; D043262:Ribonuclease P