SEQUENCE AND EXPRESSION PATTERN OF THE DROSOPHILA-MELANOGASTER MITOCHONDRIAL PORIN GENE - EVIDENCE OF A CONSERVED PROTEIN DOMAIN BETWEEN FLY AND MOUSE

We have recently cloned a cDNA encoding mitochondrial porin in Drosoph ila melanogaster and shown its chromosomal localization (Messina et al ,, FEBS Lett, (1996) 384, 9-13), Such cDNA was used as a probe for scr eening a genomic library. We thus cloned and sequenced a 4494-bp genom ic region which contained the whole gene for the mitochondrial porin o r VDAC, It was found that this D, melanogaster porin gene contains fiv e exons, numbered IA (115 bp), IB (123 bp), II (320 bp), III (228 bp) and IV (752 bp), The exons II, III and IV contain the protein coding s equence and the 3' untranslated sequence (3'-UTR), The first base in e xon II precisely corresponds to the first base of the starting ATG cod on, Exon IA corresponds to the 5'-UTR sequence reported in the publish ed cDNA sequence. Exon IB corresponds to an alternative 5'-UTR sequenc e, demonstrated to be transcribed by 5'-RACE experiments, The exon-int ron splicing borders and the length of the exon III perfectly match a homologous internal exon detected in the mouse genes. Such exon encode s a protein domain predicted by sequence transmembrane arrangement mod els to contain major hydrophilic loops and it is thus suspected to hav e a conserved distinct function. In situ hybridization experiments con firmed the localization of the genomic clone on the chromosome 2L at r egion 32B3-4. Together with genomic Southern blotting at various strin gencies, the same experiment did not confirm the presence of a second genetic locus on D, melanogaster chromosomes. Northern blots demonstra ted that the porin gene is a housekeeping one: three messages of appro x, 1.21.6 kbp are transcribed in every fly developmental stage that wa s studied, They were shown to derive by an alternative usage of differ ent promoters and polyadenylation sites. (C) 1998 Federation of Europe an Biochemical Societies.