Structure and regulation of a nuclear gene in Saccharomyces cerevisiae that specifies MRP13, a protein of the small subunit of the mitochondrial ribosome.
AUTOR(ES)
Partaledis, J A
RESUMO
MRP13 is defined by biochemical criteria as a 35-kilodalton small subunit protein of the yeast mitochondrial ribosome. The MRP13 gene was identified by immunological screening of a yeast genomic library in lambda gt11 and a functional copy of the gene has been cloned on a 2.2-kilobase BglII fragment. Sequencing of this fragment showed that the MRP13 coding region specifies a 324-amino-acid basic protein with a calculated Mr of 37,366. Computer searches failed to reveal any significant sequence similarity to previously identified ribosomal proteins or to the sequences in the current National Biomedical Research Foundation data base. Cells carrying disrupted copies of MRP13 lacked the MRP13 protein but were not impaired in either mitochondrial protein synthesis or assembly of 37S ribosomal subunits, indicating that, like L29 and L30 in Escherichia coli (M. Lotti, E. R. Dabbs, R. Hasenbank, M. Stöffler-Meilicke, and G. Stöffler, Mol. Gen. Genet. 192:295-300, 1983), MRP13 is not essential for ribosome synthesis or function. Analysis of the sequence in the MRP13 5'-flanking region revealed the closely linked gene for the cytoplasmic ribosomal protein rp39A. The rp39A coding region began at nucleotide -846 and ended at -325 with respect to the MRP13 translational start. The steady-state levels of the MRP13 mRNA were determined in response to carbon catabolite repression, variation in the mitochondrial genetic background, and increased gene dosage of MRP13. In [rho+] cells, transcript levels were repressed severalfold by growth in glucose compared with growth in either galactose or nonfermentable carbon sources. In respiratory-deficient strains ([rho0], [mit-]), however, transcription appeared to be largely derepressed even in the presence of high concentrations of glucose. Despite high levels of the MRP13 transcripts in [rho0] cells, the MRP13 protein did not accumulate, suggesting that the protein is relatively unstable in the absence of ribosome assembly. Cells carrying the MRP13 gene on a multiple-copy plasmid overproduced the mRNA in rough proportion to the gene dosage and the protein in a significant but lesser amount. The results indicate that MRP13 expression is regulated predominantly at the transcriptional level in response to catabolite repression and the cellular capacity for respiration and, in addition, that protein levels appear to be modulated posttranscriptionally by degradation of free copies of the MRP13 protein.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=365420Documentos Relacionados
- Structure and regulation of a nuclear gene in Saccharomyces cerevisiae that specifies MRP7, a protein of the large subunit of the mitochondrial ribosome.
- Cloning and analysis of the nuclear gene for YmL33, a protein of the large subunit of the mitochondrial ribosome in Saccharomyces cerevisiae.
- Characterization of an SNR gene locus in Saccharomyces cerevisiae that specifies both dispensible and essential small nuclear RNAs.
- Regulation of nuclear genes encoding mitochondrial proteins in Saccharomyces cerevisiae.
- Primary structure of the nuclear PUT2 gene involved in the mitochondrial pathway for proline utilization in Saccharomyces cerevisiae.