title: Nam1p, a protein involved in RNA processing and translation, is coupled to transcription through an interaction with yeast mitochondrial RNA polymerase.
abstract: Alignment of three fungal mtRNA polymerases revealed conserved amino acid sequences in an amino-terminal region of the Saccharomyces cerevisiae enzyme implicated previously as harboring an important functional domain. Phenotypic analysis of deletion and point mutations, in conjunction with a yeast two-hybrid assay, revealed that Nam1p, a protein involved in RNA processing and translation in mitochondria, binds specifically to this domain. The significance of this interaction in vivo was demonstrated by the fact that the temperature-sensitive phenotype of a deletion mutation (rpo41Delta2), which impinges on this amino-terminal domain, is suppressed by overproducing Nam1p. In addition, mutations in the amino-terminal domain result specifically in decreased steady-state levels of mature mitochondrial CYTB and COXI transcripts, which is a primary defect observed in NAM1 null mutant yeast strains. Finally, one point mutation (R129D) did not abolish Nam1p binding, yet displayed an obvious COX1/CYTB transcript defect. This mutation exhibited the most severe mitochondrial phenotype, suggesting that mutations in the amino-terminal domain can perturb other critical interactions, in addition to Nam1p binding, that contribute to the observed phenotypes. These results implicate the amino-terminal domain of mtRNA polymerases in coupling additional factors and activities involved in mitochondrial gene expression directly to the transcription machinery.
authors: Department of Biochemistry, Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia 30322, USA.
authors: M S
authors: MS
authors: Rodeheffer
authors: B E
authors: BE
authors: Boone
authors: A C
authors: AC
authors: Bryan
authors: G S
authors: GS
authors: Shadel
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D012313:RNA / Q000378:metabolism*; D000077278:RNA, Mitochondrial; D020449:Repetitive Sequences, Amino Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
chemical_list: C063626:MTF2 protein, S cerevisiae; D024101:Mitochondrial Proteins; D000077278:RNA, Mitochondrial; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012313:RNA; D012321:DNA-Directed RNA Polymerases