Caracterizacao parcial da estrutura molecular e supramolecular de genes cyp3a de rato Expressao especifica hepatica

The cytochromes P450 constitute a super family of genes which, in mammalian organisms, are selectively expressed in a tissue specific manner, depending on the developmental stage, hormonal status and also on the presence of endogenous and exogenous agents. In recent years, cloning experiments of several P450 genes, provided new information regarding its molecular diversity as well as on the genetic relationships between different family members. The clarification of the mechanisms that underlay the control of its transcriptional activity has also relied on the cloning of genomic DNA, as a starting point for the structural and functional analysis of these genes. In this work, our aim was to investigate the specificity of tissue expression of two P450 cytochrome genes, whose products had been previously identified in rat liver, and that are known to represent the isoenzymes cyp3a1 and cyp3a2. The rationale was that, despite a high degree of structural homology between cyp3a1 and cyp3a2 cDNA, they show distinct constitutive and induced expression patterns. The presence of the respective mRNAs was analysed in ten different tissues: adrenal gland, bladder, brain, stomach, intestine, nasal mucosa, testis, thymus, liver and lung. Our results showed that these genes are not expressed in extra-hepatic tissues, even in the presence of inducer such as dexamethasone or phenobarbital. In order to investigate the regulation of cyp3a1 and cyp3a2 expression, we proceed to the cloning of the respective genes in a rat liver genomic library, constructed in Embl3cosW / E. coli NM626. One million of recombinants were screened with cDNA and oligonucleotide probes specific for CYP3A genes. Two clones of 26 and 24 kb were selected and named cosCYP / 3A1, respectively. The partial sequencing analysis of the 5 regions, proximal to the transcription initiation site, revealed the existence of homology between these two clones and the allelic variant of cyp3a1 and the cyp3a2 cDNA, respectively..Available from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga