Cloning and analysis of unique human glutaminase isoforms generated by tissue-specific alternative splicing.
Three human glutaminase (hGA) isoforms were identified, two of which represent isoforms previously unidentified in any species. One isoform contains an open reading frame with high homology with the rat kidney-type glutaminase, suggesting that this isoform represents the human kidney-type glutaminase, hKGA. A second isoform, termed hGAC, contains an open reading frame that matches hKGA except for a unique COOH-terminal amino acid sequence. In addition, a third human glutaminase isoform was identified from a computer search and on further analysis was found to represent an additional unique isoform, hGAM. hKGA is expressed predominantly in brain and kidney but not in liver, hGAC is expressed principally in cardiac muscle and pancreas but not in liver or brain, and hGAM is expressed solely in cardiac and skeletal muscle. hGAC is the predominant isoform expressed by a human breast cancer cell line that exhibits a high rate of glutamine utilization and glutaminase activity. Genomic Southern analysis as well as isolation and analysis of five glutaminase genomic clones suggested that all three hGA isoforms originate from the same locus and therefore represent mRNA species that are produced by tissue-specific alternative splicing of a single pre-mRNA. Furthermore, an RT-PCR assay was developed that can be used to easily differentiate between hKGA and hGAC mRNA species.
Elgadi
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Surgical Oncology Research Laboratories, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Meguid
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Qian
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Souba
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Abcouwer
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D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D005972:Glutaminase / Q000235:genetics*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D007527:Isoenzymes; D012333:RNA, Messenger; D005972:Glutaminase