Three N-terminal variants of the AE2 Cl-/HCO3- exchanger are encoded by mRNAs transcribed from alternative promoters.
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.
Wang
Z
Z
Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Ohio 45267-0524, USA.
Schultheis
P J
PJ
Shull
G E
GE
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D027321:Anion Transport Proteins; D017920:Antiporters; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D017931:DNA Primers; D005091:Exons; D005753:Gastric Mucosa / Q000378:metabolism; D014644:Genetic Variation; D007438:Introns; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics*; D008715:Methionine; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism*; D019105:Random Amplified Polymorphic DNA Technique; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D064606:SLC4A Proteins; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D027321:Anion Transport Proteins; D017920:Antiporters; D017931:DNA Primers; D008565:Membrane Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D064606:SLC4A Proteins; D008715:Methionine