RESUMO
alpha-Fetoprotein (AFP) is a serum protein expressed during fetal life, the expression of which is shut off after birth. The activity of the mouse Afp gene promoter region comprised between -80 and -38 bp is regulated by the thyroid hormone receptor (T3R): negatively in the presence of T3 and positively in the absence of T3. The stimulating effect of unliganded T3R is, unexpectedly, antagonized by cofactors that have histone-acetyl-transferase activity, or by sodium butyrate, which inhibits histone acetylases (HDACs). The unliganded T3R stimulating activity effect is thus associated with protein deacetylation, contrary to the usual situation. In combination with previous results, our observations suggest that T3-mediated down regulation of the Afp promoter is due to T3-induced protein acetylation leading to loss of a nucleosomal structure (required for promoter activity) and chromatin opening.
Assuntos
Proteínas de Ligação a DNA , Proteínas Nucleares , Regiões Promotoras Genéticas , Receptores dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos/fisiologia , alfa-Fetoproteínas/genética , alfa-Fetoproteínas/metabolismo , Sequência de Bases , Células Cultivadas , Regulação para Baixo , Ensaio de Desvio de Mobilidade Eletroforética , Regulação da Expressão Gênica , Fator 1 Nuclear de Hepatócito , Fator 1-alfa Nuclear de Hepatócito , Fator 1-beta Nuclear de Hepatócito , Inibidores de Histona Desacetilases , Histona Desacetilases/metabolismo , Humanos , Luciferases/metabolismo , Dados de Sequência Molecular , Mutação , Reação em Cadeia da Polimerase , Hormônios Tireóideos/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição GênicaRESUMO
SP6 belongs to the SP/KLF family of transcription factors, characterized by a DNA-binding domain composed of three zinc fingers of the C(2)H(2) type. The Sp6 gene generates two different transcripts, termed Sp6 and epiprofin, which differ in the first exon and encode the same SP6 protein. These transcripts are mainly expressed in the skin, the teeth, and the limb buds of embryos and also in the adult lungs. To gain insight into the biological function of the SP6 protein, we knocked out the gene by eliminating the full coding region. The resulting Sp6 null mice are nude, lack functional teeth, and present limb and lung malformations. We also showed that the identified abnormalities are associated with apoptotic misregulations. In conclusion, this work indicates that Sp6 plays a critical role in the development of several epithelium-containing organs or appendages, possibly by regulating apoptosis.
Assuntos
Anormalidades Congênitas , Fatores de Transcrição Kruppel-Like/metabolismo , Morfogênese/genética , Alopecia/genética , Animais , Apoptose/fisiologia , Epiderme/anormalidades , Extremidades/crescimento & desenvolvimento , Extremidades/patologia , Regulação da Expressão Gênica no Desenvolvimento , Fatores de Transcrição Kruppel-Like/genética , Deformidades Congênitas dos Membros , Camundongos , Camundongos Knockout , Morfogênese/fisiologia , Polidactilia/genética , Alvéolos Pulmonares/citologia , Alvéolos Pulmonares/patologia , Sindactilia/genética , Dente/crescimento & desenvolvimento , Dente/fisiologia , Anormalidades DentáriasRESUMO
The alpha-fetoprotein gene (Afp) is a member of a multigenic family that comprises the related genes encoding albumin, alpha-albumin, and vitamin D binding protein. The biological role of this major embryonic serum protein is unknown although numerous speculations have been made. We have used gene targeting to show that AFP is not required for embryonic development. AFP null embryos develop normally, and individually transplanted homozygous embryos can develop in an AFP-deficient microenvironment. Whereas mutant homozygous adult males are viable and fertile, AFP null females are infertile. Our analyses of these mice indicate that the defect is caused by a dysfunction of the hypothalamic/pituitary system, leading to anovulation.