Identification of a human cytoplasmic poly(A) nuclease complex stimulated by poly(A)-binding protein.
The poly(A) tail shortening in mRNA, called deadenylation, is the first rate-limiting step in eukaryotic mRNA turnover, and the polyadenylate-binding protein (PABP) appears to be involved in the regulation of this step. However, the precise role of PABP remains largely unknown in higher eukaryotes. Here we identified and characterized a human PABP-dependent poly(A) nuclease (hPAN) complex consisting of catalytic hPan2 and regulatory hPan3 subunits. hPan2 has intrinsically a 3' to 5' exoribonuclease activity and requires Mg2+ for the enzyme activity. On the other hand, hPan3 interacts with PABP to simulate hPan2 nuclease activity. Interestingly, the hPAN nuclease complex has a higher substrate specificity to poly(A) RNA upon its association with PABP. Consistent with the roles of hPan2 and hPan3 in mRNA decay, the two subunits exhibit cytoplasmic co-localization. Thus, the human PAN complex is a poly(A)-specific exoribonuclease that is stimulated by PABP in the cytoplasm.
Uchida
Naoyuki
N
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.
Hoshino
Shin-Ichi
S
Katada
Toshiaki
T
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D017173:Caenorhabditis elegans; D002384:Catalysis; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004331:Drosophila melanogaster; D005095:Exoribonucleases / Q000737:chemistry / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013997:Time Factors; D014162:Transfection
D004247:DNA; D005095:Exoribonucleases; D008274:Magnesium; D039102:Poly(A)-Binding Proteins; D012313:RNA; D012333:RNA, Messenger; D011994:Recombinant Proteins