RESUMO
We have cloned and sequenced, in both mouse and human, regions of the HOX-4 complex which contain two Abd-B like genes, Hox-4.4 and Hox-4.5 (HOX4C and HOX4D in human, respectively). The high degree of conservation between the homeoprotein sequences extends to non-coding areas, which suggests that the mechanisms of regulation have been conserved. We show that the Hox-4.5/Hox-4.4 intergenic region can be broadly subdivided into three domains based on DNA conservation between rodents and primates. The presence of all these domains in association with sequences located 3' to the transcription termination site are required to mimick the spatial regulation of Hox-4.4 in transgenic mouse embryos. Several highly conserved short sequences located in this region were studied in gel retardation assays for their binding to potential regulatory factors. One such factor is detected in embryonal carcinoma cells but absent from other differentiated cell lines. This specific binding activity is down regulated upon retinoic acid treatment.
Assuntos
Evolução Biológica , Regulação da Expressão Gênica , Genes Homeobox , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , DNA/genética , Feto/fisiologia , Biblioteca Gênica , Humanos , Camundongos , Camundongos Transgênicos , Dados de Sequência Molecular , Proteínas Recombinantes de Fusão/metabolismo , Mapeamento por Restrição , Homologia de Sequência do Ácido Nucleico , beta-Galactosidase/genética , beta-Galactosidase/metabolismoRESUMO
We analyzed the expression of the c-erbA proto-oncogene in different tissues of chicken embryos. c-erbA transcripts were found at low levels in the lung, kidney, liver, and heart and in high amounts in embryonic blood cells. Nuclease mapping assays proved that these transcripts were true c-erbA transcripts. In situ hybridization on fractionated embryonic blood cells showed that c-erbA transcripts were predominantly found in erythroblasts, particularly during the final step of differentiation. Life span analysis of c-erbA mRNAs revealed their relative instability, demonstrating that the high level of c-erbA transcripts in embryonic erythroblasts was not the result of passive accumulation. These results suggest that the c-erbA genes play some role in erythrocyte differentiation.