The NAM1 protein (NAM1p), which is selectively required for cox1, cytb and atp6 transcript processing/stabilisation, is located in the yeast mitochondrial matrix.
The NAM1 nuclear gene was shown to control the stability and/or processing of mitochondrial transcripts of the cytochrome b, cytochrome oxidase subunit I and ATP synthase subunit VI genes [Groudinsky O., Bousquet I., Wallis M. G., Slonimski, P. P. & Dujardin G. (1993) Mol. Gen. Genet. 240, 419-427]. In order to better understand the mode of action of the NAM1 gene product, we have examined its intracellular fate. A fusion plasmid enabling bacterial over-expression of the corresponding protein-A-NAM1 cognate was constructed and subsequently employed as an antigen to raise polyclonal antibodies. These antibodies specifically recognise a 50-kDa protein which purifies along with the mitochondria and corresponds to NAM1p. Submitochondrial localisation experiments show that NAM1p is a soluble protein, located interior to the mitoplasts. Matricial location is a strong argument in favour of a direct interaction of NAM1p with particular mitochondrial transcripts and leads us to propose a model in which NAM1p could be an RNA-convoying protein stabilising and directing mitochondrial transcripts towards the inner face of the inner membrane where translation and assembly seem to occur.
Wallis
M G
MG
Centre de Génétique Moléculaire du CNRS, Université Paris VI, Gif sur Yvette, France.
Groudinsky
O
O
Slonimski
P P
PP
Dujardin
G
G
D001483:Base Sequence; D003573:Cytochrome b Group / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D006180:Proton-Translocating ATPases / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013367:Submitochondrial Particles / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
D003573:Cytochrome b Group; D005656:Fungal Proteins; C063626:MTF2 protein, S cerevisiae; D024101:Mitochondrial Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D003576:Electron Transport Complex IV; D006180:Proton-Translocating ATPases