Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have isolated cDNAs encoding a cardiac variant of the AE3 Cl-/HCO3- exchanger from a rat heart library. The predicted cardiac AE3 polypeptide is 1030 amino acids in length, while the AE3 variant expressed in brain consists of 1227 amino acids. The C-terminal 957 amino acids of both polypeptides are identical, but the cardiac protein contains a unique N-terminal sequence of 73 amino acids which replaces the first 270 amino acids of the brain form. To determine the genetic basis for the differences between the cardiac and brain AE3 variants, we isolated and characterized the rat gene. Exons 1-6 contain the 5'-untranslated sequence and the first 270 codons of the brain mRNA, while exons 7-23 contain the coding and 3'-untranslated sequences which are common to the brain and cardiac mRNAs. The 5'-untranslated and unique N-terminal coding sequences of the cardiac mRNA are contained within a single exon, termed C1, which forms part of the intron between exons 6 and 7 of the brain transcription unit. Primer extension and S1 nuclease protection assays demonstrate that transcription of the cardiac AE3 mRNA precursor is intiaited within this intron. Therefore, alternative promoter and exon usage are involved in generation of the two AE3 mRNAs.
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PMID:The predicted translation product of a cardiac AE3 mRNA contains an N terminus distinct from that of the brain AE3 Cl-/HCO3- exchanger. Cloning of a cardiac AE3 cDNA, organization of the AE3 gene, and identification of an alternative transcription initiation site. 156 21

We have previously shown that the rat kidney band 3 Cl-/HCO3- exchanger mRNA encodes an NH2-terminal truncated form of band 3 and that its 5' end differs from that of the erythrocyte band 3 mRNA (K. E. Kudrycki and G. E. Shull. J. Biol. Chem. 264: 8185-8192, 1989). To determine the genetic basis for the alternative kidney and erythroid mRNAs, we 1) isolated and characterized a rat erythroid band 3 cDNA, 2) isolated the rat band 3 gene and determined the exon/intron organization of sequences corresponding to the alternative 5' ends of the rat kidney and erythroid mRNAs, and 3) identified the transcription initiation sites of the two transcripts. The unique sequences at the 5' end of the rat erythroid mRNA are derived from exons 1-3 and are followed directly by sequences from exon 4 that are common to both mRNAs. In the kidney mRNA, sequences upstream of exon 4 are derived entirely from intron 3. Primer extension and S1 nuclease protection analyses demonstrate the presence of multiple transcription initiation sites for the rat erythroid band 3 mRNA at the beginning of exon 1, whereas the transcription initiation site for the kidney mRNA is located within intron 3. Thus two distinct promoters, separated by almost 5 kb of genomic sequence, are responsible for the highly tissue-specific transcription of the alternative rat erythroid and kidney band 3 mRNAs.
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PMID:Rat kidney band 3 Cl-/HCO3- exchanger mRNA is transcribed from an alternative promoter. 845 65

Multiple AE2 Cl-/HCO3- exchanger mRNAs have been identified in rat. To determine the genetic basis for these mRNAs and whether they encode different variants of the exchanger, we used both rapid amplification of cDNA ends and S1 nuclease protection protocols and examined the organization of the gene. mRNAs encoding three N-terminal variants of AE2 (AE2a, AE2b, and AE2c) were identified and shown to be transcribed from alternative promoters. The AE2a transcription unit consists of 23 exons, with exons 1 and 2 containing 5'-untranslated sequence and the first 17 codons. The first exon of AE2b is located in intron 2; it contains 5'-untranslated sequence and an alternative 3-amino acid N-terminal coding sequence and is spliced to exon 3. The first exon of AE2c is located in intron 5; it consists of 5'-untranslated sequence and is spliced to exon 6, which contains the translation initiation codon corresponding to Met-200 of AE2a. Northern analysis shows that AE2a is expressed in all tissues, AE2b exhibits a more restricted distribution with highest levels in stomach, and AE2c is expressed only in stomach. Thus, the use of alternative promoters leads to the production of three N-terminal variants of AE2 that exhibit tissue-specific patterns of expression.
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PMID:Three N-terminal variants of the AE2 Cl-/HCO3- exchanger are encoded by mRNAs transcribed from alternative promoters. 863 28