title: Tissue expression and translational control of rat kynurenine aminotransferase/glutamine transaminase K mRNAs.
abstract: Kynurenic acid (KA) is an endogenous glutamate receptor antagonist at the level of the different ionotropic glutamate receptors. One of the enzymes responsible for the production of KA, kynurenine aminotransferase I (KATI), also catalyses the reversible transamination of glutamine to oxoglutaramic acid (GTK, EC 2.6.1.15). The enzyme exists in a cytosolic and in a mitochondrial form because of the presence of two different KATI mRNAs coding for a protein respectively with and without leader sequence targeting the protein into mitochondria. We have cloned from a phage library of rat kidney cDNA four new KATI cDNAs containing different 5' untranslated regions (UTRs). One of the transcripts (+14KATI cDNA) contains an alternative site of initiation of translation. The tissue distribution of the different transcripts was studied by RT-PCR. The study demonstrated that several KATI mRNAs are constitutively expressed in ubiquitous manner, while +14KATI mRNA is present only in kidney. The translational efficiency of the different transcripts was studied in vitro and enzymatic activities were measured in transiently transfected Cos-1 cells. Each KATI mRNA exhibits a different in vitro translational efficiency, which corresponds to different levels of KAT enzymatic activity in transfected cells. Both findings correlate with the predicted accessibility of the ribosomal binding sites of the different mRNAs. The structure of the rat KATI/GTK gene was also studied. The expression of several KATI mRNAs with different 5'UTRs represents an interesting example of transcriptional/translational control on the expression of pyridoxal phosphate (PLP)-dependent aminotransferases.
authors.affiliation: CNS Preclinical Research and Biotechnology Department, Pharmacia SpA, Viale Pasteur 10, 20014 Nerviano (MI), Italy. monica.mosca@pharmacia.com
authors.forename: Monica
authors.initials: M
authors.lastname: Mosca
authors.forename: Cristina
authors.initials: C
authors.lastname: Croci
authors.forename: Marina
authors.initials: M
authors.lastname: Mostardini
authors.forename: Jerome
authors.initials: J
authors.lastname: Breton
authors.forename: Jan
authors.initials: J
authors.lastname: Malyszko
authors.forename: Nilla
authors.initials: N
authors.lastname: Avanzi
authors.forename: Salvatore
authors.initials: S
authors.lastname: Toma
authors.forename: Luca
authors.initials: L
authors.lastname: Benatti
authors.forename: Silvia
authors.initials: S
authors.lastname: Gatti
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D001665:Binding Sites; D015152:Blotting, Northern; D019556:COS Cells; D003001:Cloning, Molecular; D003360:Cosmids; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005786:Gene Expression Regulation; D015723:Gene Library; D007668:Kidney / Q000378:metabolism; D008190:Lyases / Q000096:biosynthesis* / Q000235:genetics; D008957:Models, Genetic; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution; D000637:Transaminases / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D020121:5' Untranslated Regions; D018076:DNA, Complementary; D020033:Protein Isoforms; D012333:RNA, Messenger; D011994:Recombinant Proteins; D004247:DNA; D000637:Transaminases; C427605:glutamine - phenylpyruvate transaminase; C021481:kynurenine-oxoglutarate transaminase; D008190:Lyases