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A new assembly pathway in the mitochondrial intermembrane space for mammalian polynucleotide phosphorylase
Author(s) -
Glavin Jenny D,
Rainey Robert N.,
Chen HsiaoWen,
Teitell Michael A.,
Koehler Carla M.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.lb62-b
Subject(s) - polynucleotide phosphorylase , intermembrane space , exoribonuclease , biology , exosome complex , microbiology and biotechnology , biogenesis , mitochondrial intermembrane space , chaperone (clinical) , purine nucleoside phosphorylase , biochemistry , rna , rnase p , enzyme , bacterial outer membrane , gene , escherichia coli , purine , medicine , pathology
Mammalian polynucleotide phosphorylase (PNPase) is an evolutionarily conserved 3′ to 5′ RNA exonuclease related to RNase PH that is involved in mRNA degradation in bacteria and chloroplasts. Recently, we showed that PNPase is localized as a peripheral membrane protein to the mitochondrial intermembrane space (IMS), a surprising location for an RNA processing enzyme since this compartment is devoid of RNA, and is released from the IMS upon serum starvation and tBID treatment (French et al., 2005). Here, we have characterized the assembly pathway of PNPase via in organello import assays and heterologous expressions studies in S. cerevisiae and identified a new import pathway for PNPase biogenesis. Processing of PNPase is defective in yeast strains containing either temperature‐sensitive mutations in the matrix processing protease (MPP, mas1 and mas2) or full and point mutation deletions of the i‐AAA protease yme1. N‐terminal sequencing reactions of PNPase purified from cultured cells or PNPase processed with recombinant MPP showed that PNPase is cleaved in a one‐step cleavage by MPP. Yme1p functions as an ATP‐driven chaperone to pull PNPase into the intermembrane space and potentially mediate folding and assembly. Yme1p has been implicated in a broad range of mitochondrial functions, including apoptosis, but until now no other known role besides degradation of misfolded membrane proteins had been assigned to this protease. Thus, we have identified a new pathway by which MPP and Yme1p coordinate to mediate the import of PNPase. We are investigating if other apoptotic proteins may utilize Yme1p for biogenesis in the mitochondrion. This work is supported by R21DC006663, R01CA74929 and R01CA107300)