부산대학교 도서관

RNase MRP is a ribonucleoprotein particle (RNP) with endoribonucleolytic activity which is involved in the processing of pre-rRNA at site A₃. A genetic screen for mutants which are synthetic lethal (sl) with a temperature sensitive (ts) mutation in the RNA component of RNase MRP (rrp2-1) has been performed in order to identify new gene products which physically and/or functionally interact with RNase MRP. Analysis of the obtained sl mutant strains led to the identification of a new and essential gene, POP3. 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. Primary tRNA transcripts accumulate, as well as spliced but 5' and 3' unprocessed pre-tRNAs. The Pop3p depletion phenotypes resemble 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 efficiently co-precipitates the RNA components of both RNase MRP and RNase P. Thus, Pop3p is a common component of both RNPs and is required for the function of both enzymes in vivo. Strain SL158 carried a mutation in HAL2 which is sl in combination with rrp2-1. Hal2p is an enzyme that converts pAp (adenosine 3', 5' bisphosphate), a product of sulfate assimilation, into 5' AMP and P_i.