Drosophila sn-glycerol-3-phosphate dehydrogenase isozymes are generated by alternate pathways of RNA processing resulting in different carboxyl-terminal amino acid sequences.
Glycerol-3-phosphate dehydrogenase (GPDH, Ec 1.1.1.8) in Drosophila melanogaster consists of a family of three isozymes designated as GPDH-1, 2, and 3 which exhibit a unique temporal and tissue-specific pattern of expression. While each isozyme is encoded by the same structural gene, they differ by the amino acid sequence at the COOH-terminal end, with GPDH-3 having the sequence Asn-His-Pro-Glu-His-Met-COOH and with GPDH-1 extended by the three amino acid sequence Glu-Asn-Leu-COOH. We have isolated both genomic and cDNA clones in order to examine the structure of the 3'-end of this gene and its transcriptional products. This analysis has demonstrated three classes of transcripts, each differing in the 3'-untranslated region and coding for an enzyme with a different COOH-terminal amino acid sequence. Each transcript is shown to arise through the differential expression of three isotype-specific exons at the 3'-end of the gene. We propose a model where the expression of each isotype-specific transcript is controlled through a developmentally regulated process of 3'-end formation and alternate splicing pathways of the pre-mRNA. Furthermore, since each transcript and its cognant isozyme is tissue-specific in expression, this model suggests a role for tissue-specific trans-acting factors in these processing events.
Cook
J L
JL
Department of Genetics, North Carolina State University, Raleigh 27695-7614.
Bewley
G C
GC
Shaffer
J B
JB
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004331:Drosophila melanogaster / Q000201:enzymology / Q000235:genetics*; D005796:Genes; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics*; D008969:Molecular Sequence Data; D014158:Transcription, Genetic
D007527:Isoenzymes; D005993:Glycerolphosphate Dehydrogenase; D004262:DNA Restriction Enzymes