RESUMO
By combining the polymerase chain reaction and differential library screening, a cDNA for an mRNA expressed in chicken avian myeloblastosis virus (AMV)-transformed monoblasts was isolated. This mRNA is not expressed in erythroblast or T-lymphoblast cell lines. Induced differentiation of the cells of the AMV-transformed BM2 line was associated with reduced levels of this transcript. The predicted protein product of Chox M was a homeodomain factor similar to murine Hox-4.3.
Assuntos
Vírus da Mieloblastose Aviária/genética , Transformação Celular Viral/genética , DNA/genética , Genes Homeobox/genética , Leucemia Mieloide Aguda/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Galinhas , Clonagem Molecular , Leucemia Mieloide Aguda/patologia , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Reação em Cadeia da Polimerase , Células Tumorais CultivadasRESUMO
The myeloperoxidase (MPO) gene is selectively expressed during haemopoiesis in the granulocytic lineage. Compared with the erythroid (beta-globin) and B-cell (immunoglobulin) lineages, little is known of the regulatory sequences and transcription factors involved in the regulation of genes specific for granulopoiesis. We have approached this issue by identifying a strong enhancer for the murine MPO gene. A candidate enhancer region was mapped by the detection of a strong DNase I hypersensitive site, -3.4 to -3.2 kb upstream of the MPO gene. A 301 bp fragment encompassing the DNase I site was shown to have strong enhancer function in a transient assay following transfection of a reporter gene into a MPO-expressing cell (WEHI 3BD+), but was inactive in lymphoid cells. Analysis of sub-fragments revealed that the whole 301 bp fragment is required for maximal enhancer function.
Assuntos
Medula Óssea/patologia , Elementos Facilitadores Genéticos , Hematopoese/genética , Peroxidase/genética , Animais , Sequência de Bases , Mapeamento Cromossômico , Leucemia Mielomonocítica Aguda/genética , Leucemia Mielomonocítica Aguda/patologia , Camundongos , Dados de Sequência Molecular , TransfecçãoRESUMO
This paper describes the characterisation of a novel chicken homeobox gene, Prh, whose encoded homeodomain sequence differs significantly from those of other factors which have been described. As expected, a portion of the encoded protein, containing the homeodomain, is capable of sequence-specific DNA-binding. Outside the homeodomain, Prh, possesses an N-terminal region extremely rich in proline residues and a C-terminal acidic portion, either of which may function as transcription regulatory domains. Since, among the chicken tissues tested, its transcription is restricted to haematopoietic cells, lung and liver, it may function in tissue-specific patterns of gene regulation. Human and murine Prh homologues have also been identified; so it is likely that such genes are a general feature of vertebrate genomes.
Assuntos
Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Genes Homeobox , Células-Tronco Hematopoéticas/metabolismo , Proteínas de Homeodomínio , Fígado/metabolismo , Pulmão/metabolismo , Sequência de Aminoácidos , Animais , Vírus da Mieloblastose Aviária/fisiologia , Sequência de Bases , Northern Blotting , Linhagem Celular , Transformação Celular Viral , Embrião de Galinha , DNA , Desoxirribonucleases/metabolismo , Humanos , Dados de Sequência Molecular , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido Nucleico , Fatores de Transcrição , Vertebrados/genéticaRESUMO
The properties of avalanche photodiodes and associated electronics required for photon counting in the Geiger and the sub-Geiger modes are reviewed. When the Geiger mode is used, there are significant improvements reported in overall photon detection efficiencies (approaching 70% at 633 nm), and a timing jitter (under 200 ps) is achieved with passive quenching at high overvoltages (20-30 V). The results obtained by using an active-mode fast quench circuit capable of switching overvoltages as high as 15 V (giving photon detection efficiencies in the 50% range) with a dead time of less than 50 ns are reported. Larger diodes (up to 1 mm in diameter) that are usable in the Geiger mode and that have quantum efficiencies over 80% in the 500-800-nm range are also reported.