RESUMO
The long-term outcome of children with TEL-AML1-positive acute lymphoblastic leukemia (ALL) is uncertain. Although studies of newly diagnosed cases have indicated that the TEL-AML1 fusion confers a favorable prognosis, analyses of relapsed cases have suggested that this may not be true. Because of treatment implications for this subgroup of patients, we have now analyzed 49 cases of relapsed ALL for the presence of TEL-AML1. Only 10% of these cases expressed the fusion, compared to 20-25% of newly diagnosed ALL cases. Additional follow-up of the cohort of 48 newly diagnosed patients with the TEL-AML1 fusion previously reported showed that the 10-year cumulative risk of relapse was 9 +/- 5% (s.e.). Together, these results suggest an excellent outcome for TEL-AML1-positive ALL.
Assuntos
Proteínas de Neoplasias/genética , Proteínas de Fusão Oncogênica , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Criança , Pré-Escolar , Estudos de Coortes , Subunidade alfa 2 de Fator de Ligação ao Core , Feminino , Seguimentos , Humanos , Masculino , Proteínas de Neoplasias/análise , Fenótipo , Leucemia-Linfoma Linfoblástico de Células Precursoras/sangue , Leucemia-Linfoma Linfoblástico de Células Precursoras/mortalidade , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Prognóstico , Recidiva , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sobrevida , Fatores de TempoRESUMO
Chlamydiae are parasitic bacteria characterized by a temporally regulated developmental cycle. In the early stage of the cycle, metabolically inert elementary bodies reorganize to dividing reticulate bodies, a process about which little is known. The purpose of this investigation was to identify and clone chlamydial genes that are expressed preferentially during the early stage of the developmental cycle of Chlamydia psittaci 6BC. Several potential early genes were cloned with highly radioactive, host-free-generated RNA probes to screen a genomic library. One clone appeared to encode a gene that was particularly well expressed at 1 h postinfection. In further characterization, we found that it encodes two complete open reading frames and one partial open reading frame of 370 codons. The partial open reading frame, designated gltX, is very similar to bacterial glutamyl-tRNA synthetases and was demonstrated to be transcribed in vivo at 24 h postinfection by primer extension analysis. A lysine-rich open reading frame (LRO) of 117 codons was found upstream and divergent from gltX. The LRO lacks homology to known proteins, and we were unable to demonstrate that it is transcribed in vivo. The third open reading frame, of 182 codons, was found to be convergent with and partially overlap the LRO. It was confirmed to be preferentially expressed within the first 1.5 h of infection by Northern (RNA) blot analysis and was designated the early upstream open reading frame (EUO). Like the LRO, the EUO is not homologous to known proteins. A major potential transcription start site of the EUO was identified by primer extension analysis. However, the sequence upstream of the site does not closely resemble the consensus recognition sequences of bacterial sigma factors even though it is AT rich. The EUO is the first chlamydial gene specific to the early stage to be cloned and sequenced.
Assuntos
Proteínas de Bactérias/genética , Chlamydophila psittaci/genética , Genes Bacterianos/genética , Sequência de Aminoácidos , Sequência de Bases , Northern Blotting , Southern Blotting , Chlamydophila psittaci/crescimento & desenvolvimento , Biblioteca Gênica , Genoma Bacteriano , Glutamato-tRNA Ligase/genética , Dados de Sequência Molecular , Fases de Leitura Aberta/genética , Reação em Cadeia da Polimerase , Estrutura Secundária de Proteína , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Fatores de Tempo , Transcrição GênicaRESUMO
The incorporation of radiolabeled GTP into RNA in host-free Chlamydia trachomatis serovar L2 organisms was investigated. The incorporation was partially inhibited by rifampin and dactinomycin and hydrolyzed by RNase. RNA made by host-free chlamydiae consisted mainly of species of fewer than 800 bases in size, although 16S and 23S species were noted by agarose-gel electrophoresis. The hybridization of radiolabeled host-free RNA to restriction fragments of the gene encoding the major outer membrane protein was analyzed; all regions of the gene were transcribed. The relative intensity of hybridization of host-free RNA made by chlamydiae isolated during the middle and late stages of the developmental cycle to the DNA of clones encoding gene products known to be made at these times in vivo indicated that the temporal patterns of host-free and in vivo transcription were similar. Radiolabeled RNA from 1- and 24-h host-free Chlamydia psittaci 6BC organisms hybridized to many of the same EcoRI and BamHI restriction fragments of C. psittaci genomic DNA, although some differences could be noted. When these RNAs were used to screen a partial C. psittaci genomic library in lambda gt11, plaques were identified that reacted mainly either with 1-h RNA or with 24-h RNA. Because RNA synthesized by host-free chlamydiae appears to be developmental cycle stage specific, transcripts made by host-free chlamydiae may be convenient probes that can be used to clone developmental stage-specific chlamydial genes.
