Functional characterization of the TMLH gene: promoter analysis, in situ hybridization, identification and mapping of alternative splicing variants.
Carnitine is a molecule with well-documented pleiotropic functions whose biosynthesis involves four catalytic steps. Here, we report a detailed analysis of the expression and transcriptional control of TMLH gene, which codifies for the first enzyme of carnitine biosynthesis. TMLH maps at the extreme end of Xq28, a chromosomal region of high genomic instability. By 5' and 3' RACE, we identified and mapped two alternative 5' TMLH first exons and seven alternative 3'-splice variants, which are spread over a genomic region of about 250 kb. While the two alternative 5' exons have different expression profiles, all the 3' alternative forms are ubiquitously expressed. Reporter assays revealed that the 3'-UTRs of each TMLH isoform might influence its own expression at post-transcriptional level. In addition, we identified a highly conserved promoter region of TMLH. Functional analysis of this region showed the presence of a CpG island, whose methylation-status could control the level of TMLH transcription. Finally, by mRNA in situ hybridization, we found that TMLH expression is present at E12.5 dpc in the mouse liver, lung and brain, and is then maintained in the postnatal brain with a specific neuronal pattern. Collectively, our data highlight a tight transcriptional and post-transcriptional control of TMLH expression.
Monfregola
Jlenia
J
Institute of Genetics and Biophysics "Adriano Buzzati-Traverso" (CNR), Via P.Castellino, 111, 80131 Naples, Italy.
Napolitano
Gennaro
G
Conte
Ivan
I
Cevenini
Armando
A
Migliaccio
Carmen
C
D'Urso
Michele
M
Ursini
Matilde Valeria
MV
D020413:3' Untranslated Regions; D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002331:Carnitine / Q000096:biosynthesis; D002874:Chromosome Mapping; D041321:Chromosomes, Human, X / Q000235:genetics; D018899:CpG Islands; D017931:DNA Primers / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D014644:Genetic Variation; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic
D020413:3' Untranslated Regions; D017931:DNA Primers; D006899:Mixed Function Oxygenases; C025931:trimethyl-lysine hydroxylase; D002331:Carnitine