The yeast RNA-binding protein Rbp1p modifies the stability of mitochondrial porin mRNA.
The Saccharomyces cerevisiae RNA-binding protein Rbp1p was initially identified as a negative growth regulator; however, its function is still obscure. Here, we show that Rbp1p in cells is associated with structures that sediment at 10,000 as well as 100,000 x g. It appears microscopically as punctate signals partially localized to the perinuclear region. Over-expression of Rbp1p in yeast resulted in growth defects on nonfermentable carbon sources, suggesting a function for Rbp1p in mitochondrial biogenesis. Absence of Rbp1p increased the level of mitochondrial porin, whereas over-expression of Rbp1p, but not an N-terminally truncated form, decreased porin levels. Over-expression of Rbp1p also decreased the level of mitochondrial porin mRNA by enhancing its degradation, an effect that was dependent on all three of the Rbp1p RNA recognition motifs. In cells, the porin mRNA is associated with Rbp1p.RNP (ribonucleoprotein) complexes. In vitro binding assays showed that Rbp1p most likely interacts with a (C/G)U-rich element in the porin mRNA 3'-UTR. Based on these observations, we infer that Rbp1p has a role in negatively regulating mitochondrial porin expression post-transcriptionally.
Institute of Molecular Medicine, College of Medicine, National Taiwan University Hospital, National Taiwan University, 7 Chung Shan South Road, Taipei 100, Taiwan.
Leh-Miauh
LM
Buu
Li-Ting
LT
Jang
Fang-Jen S
FJ
Lee
D002467:Cell Nucleus / Q000502:physiology / Q000648:ultrastructure; D003001:Cloning, Molecular; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D008928:Mitochondria / Q000502:physiology*; D016133:Polymerase Chain Reaction; D018272:Porins / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism
D018272:Porins; D012331:RNA, Fungal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins