Intracellular localization of differentially regulated RNA-specific adenosine deaminase isoforms in inflammation.
Adenosine-to-inosine (A-to-I) RNA editing is a post-transcriptional process that amplifies the repertoire of protein production. Recently, the induction of this process through up-regulation of the editing enzyme RNA-specific adenosine deaminase 1 (ADAR1) was documented during acute inflammation. Here we report that the inflammation-induced up-regulation of ADAR1 involves differential production and intracellular localization of several isoforms with distinct RNA-binding domains and localization signals. These include the full-length ADAR1 (p150) and two functionally active short isoforms (p80 and p110). ADAR1 p80 starts at a methionine 519 (M519) due to alternative splicing in exon 2, which deletes the putative nuclear localization signal, the Z-DNA binding domain, and the entire RNA binding domain I. ADAR1 p110 is the mouse homologue of the human ADAR1 110-kDa variant (M246), which retains the second half of the Z-DNA binding domain, all RNA binding domains, and the deaminase domain. Additional variations are found in the third RNA binding domain of ADAR1; they are differentially regulated during inflammation, generating isoforms with different levels of activities. Studies in several cell types transfected with ADAR1-EGFP chimeras demonstrated that the p150 and p80 variants are localized in the cytoplasm and nucleolus, respectively. In agreement with this observation, endogenous ADAR1 was identified in the cytoplasm and nucleolus of mouse splenocytes and HeLa cells. Since the ADAR1 variants are differentially regulated during acute inflammation, it suggests that the localization of these variants and of A-to-I RNA editing in the cytoplasm, nucleus, and nucleolus is intracellularly reorganized in response to inflammatory stimulation.
Yang
Jing-Hua
JH
Department of Surgery and Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, USA. jinghua.yang@yale.edu
Nie
Yongzhan
Y
Zhao
Qingchuan
Q
Su
Yingjun
Y
Pypaert
Marc
M
Su
Haili
H
Rabinovici
Reuven
R
D000241:Adenosine / Q000737:chemistry; D000243:Adenosine Deaminase / Q000096:biosynthesis* / Q000737:chemistry*; D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002466:Cell Nucleolus; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D005091:Exons; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation; D007288:Inosine / Q000737:chemistry; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D020033:Protein Isoforms; D012313:RNA / Q000378:metabolism; D016601:RNA-Binding Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D013154:Spleen / Q000166:cytology; D014162:Transfection; D015854:Up-Regulation
D008164:Luminescent Proteins; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D049452:Green Fluorescent Proteins; D007288:Inosine; D012313:RNA; D008715:Methionine; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase; D000241:Adenosine