RESUMO
Three-month-old Wistar rats were fed with either an iron-deficient diet for 21 days or an iron-excessive diet for 10 days. Fifty thousand clones of a cDNA library of small intestine mucosa were hybridized with two radioactive samples synthesized on mRNA from the small intestine of rats fed with iron-excessive or iron-deficient diets. As a result, genes were found with mRNA level depending on the content of alimentary iron. Iron deficiency increased the mRNA level of genes of apolipoprotein AIV and class 1 antigen and decreased the mRNA level of the apolipoprotein AI gene and of an unknown gene, while no change was found in the mRNA level of the gene of fatty acid-binding protein. Excess of dietary iron resulted in the increase in mRNA of this gene and in a decrease in the apolipoprotein AI gene and in the unknown gene. The mRNA of apolipoprotein AIV did not change. The data indicate that changes in the level of alimentary iron influence the expression of genes involved in metabolism of lipids.
Assuntos
Expressão Gênica/efeitos dos fármacos , Mucosa Intestinal/efeitos dos fármacos , Mucosa Intestinal/metabolismo , Ferro da Dieta/administração & dosagem , Proteínas de Neoplasias , Proteínas do Tecido Nervoso , Animais , Apolipoproteína A-I/genética , Apolipoproteína C-III , Apolipoproteínas A/genética , Apolipoproteínas C/genética , Sequência de Bases , Proteínas de Transporte/genética , DNA Complementar/genética , Proteína 7 de Ligação a Ácidos Graxos , Proteínas de Ligação a Ácido Graxo , Intestino Delgado/efeitos dos fármacos , Intestino Delgado/metabolismo , Deficiências de Ferro , Masculino , Dados de Sequência Molecular , Proteína P2 de Mielina/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos WistarRESUMO
1. The bovine kappa-casein gene has been isolated as a series of overlapping lambda clones and shown to consist of five exons distributed over a total length of approximately 13 kb. Most of the mature protein-coding sequence is contained in a single large exon. 2. Approximately 65% of the gene has been sequenced together with portions of the 5'- and 3'-flanking sequences. The immediate 5'-flanking sequence contains several motifs which are characteristic of upstream regions including a TATA box, a CAAT box, a sequence similar to that recognized by transcription factor AP-1 and a purine-rich sequence resembling that found upstream in all other lactoprotein genes. Other possible regulatory sequences are found upstream of exon 4. 3. The organization of the kappa-casein gene, together with its upstream sequence, confirms previous conclusions that it is unrelated to the calcium-sensitive-casein gene family to which it is linked. Evidence is presented which supports a previous suggestion that kappa-casein and the fibrinogens are evolutionarily related. 4. Intron sequences contain several examples of the A family of the artiodactyl Alu-like repeated sequences, together with a single example of a C-family sequence. The remainders of the introns of the kappa-casein gene, compared with the repeat elements and exons, are A + T-rich. 5. Among the lambda clones isolated, representatives were found of the A and B genetic variants which can be distinguished by restriction-enzyme analysis. Several other examples of polymorphisms in the non-coding region were found.
Assuntos
Caseínas/genética , Alelos , Sequência de Aminoácidos , Animais , Sequência de Bases , Bovinos , Clonagem Molecular , Éxons , Genes , Dados de Sequência Molecular , Polimorfismo Genético , Mapeamento por RestriçãoRESUMO
The expression of casein genes in the mammary cells is regulated by peptide and steroid hormones. To investigate the controlling mechanisms we have isolated and characterized the bovine beta-casein gene. The gene has the size of 8.6 kb, which is 7.8 times longer than the corresponding mRNA composed of nine exons. The genomic clones include additional 8.5-kb and 4.5-kb sequences of the 5'- and 3'-flanking regions. We have determined the sequences of the 5' and 3' ends of the gene and compared them with the respective sequences of the rat beta-casein gene. Conserved sequences are identical or homologous to the potential binding sites for nuclear factors and for glucocorticoid and progesterone receptors. The regulatory region contains two different TATA signals and a repeat sequence between them.
