Sls1p is a membrane-bound regulator of transcription-coupled processes involved in Saccharomyces cerevisiae mitochondrial gene expression.
Mitochondrial translation is largely membrane-associated in S. cerevisiae. Recently, we discovered that the matrix protein Nam1p binds the amino-terminal domain of yeast mtRNA polymerase to couple translation and/or RNA-processing events to transcription. To gain additional insight into these transcription-coupled processes, we performed a genetic screen for genes that suppress the petite phenotype of a point mutation in mtRNA polymerase (rpo41-R129D) when overexpressed. One suppressor identified in this screen was SLS1, which encodes a mitochondrial membrane protein required for assembly of respiratory-chain enzyme complexes III and IV. The mtRNA-processing defects associated with the rpo41-R129D mutation were corrected in the suppressed strain, linking Sls1p to a pathway that includes mtRNA polymerase and Nam1p. This was supported by the observation that SLS1 overexpression rescued the petite phenotype of a NAM1 null mutation. In contrast, overexpression of Nam1p did not rescue the petite phenotype of a SLS1 null mutation, indicating that Nam1p and Sls1p are not functionally redundant but rather exist in an ordered pathway. On the basis of these data, a model in which Nam1p coordinates the delivery of newly synthesized transcripts to the membrane, where Sls1p directs or regulates their subsequent handling by membrane-bound factors involved in translation, is proposed.
Bryan
Anthony C
AC
Department of Biochemistry, Rollins Research Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Rodeheffer
Matthew S
MS
Wearn
Christopher M
CM
Shadel
Gerald S
GS
D001059:Apoproteins / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003573:Cytochrome b Group / Q000378:metabolism; D045303:Cytochromes b; D004272:DNA, Mitochondrial / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D005656:Fungal Proteins; D015870:Gene Expression / Q000502:physiology; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008928:Mitochondria / Q000235:genetics*; D024101:Mitochondrial Proteins; D012313:RNA / Q000378:metabolism; D012331:RNA, Fungal / Q000378:metabolism; D000077278:RNA, Mitochondrial; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D001059:Apoproteins; D002352:Carrier Proteins; D003573:Cytochrome b Group; D004272:DNA, Mitochondrial; D005656:Fungal Proteins; C063626:MTF2 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012331:RNA, Fungal; D000077278:RNA, Mitochondrial; C492046:SLS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012313:RNA; D045303:Cytochromes b; D012321:DNA-Directed RNA Polymerases