RESUMO
We have shown previously that a mutation of the KI-KII site immediately 5' to J(kappa)1 on the mouse immunoglobulin light chain kappa locus reduces the rearrangement level in cis, although it does not affect transcription. Here we deleted by homologous recombination in mouse embryonic stem cells a 4-kb DNA fragment, located immediately upstream of the KI-KII element, which contains the promoter of the long germline transcript. Analysis of gene-targeted heterozygous mouse splenic B cells showed a strong decrease in rearrangement for the allele bearing the deletion. When both the KI-KII mutation and the 4-kb deletion were present on the same allele, the overall reduction in rearrangement was stronger than with the 4-kb deletion alone underlying the role of these two elements in the regulation of rearrangement. The same deletion was performed by homologous recombination on one allele of the rearrangement-inducible mouse 103/bcl2-hygro(R) pre-B cell line, and resulted in a similar reduction in the induction of rearrangement of the mutated allele. This result validates this cell line as an in vitro model for studying the incidence of gene-targeted modifications of the kappa locus on the regulation of rearrangement.
Assuntos
Linfócitos B , Rearranjo Gênico do Linfócito B , Região de Junção de Imunoglobulinas/genética , Cadeias kappa de Imunoglobulina/genética , Deleção de Sequência , Alelos , Animais , Linfócitos B/citologia , Linhagem Celular , Marcação de Genes , Células Germinativas , Camundongos , Mutagênese , Transcrição GênicaRESUMO
A very unusual molecular mechanism is involved in generating the preimmune repertoire in the chicken bursa of Fabricius. A unique rearranged V gene is diversified through a program of segmental gene conversion with a pool of noncoding pseudogenes being used as donors. A specifically committed progenitor that originates in the embryonic bursa is responsible for long-term maintenance of the B cell population. Both these properties and the characteristics of the peripheral B cell compartment are discussed in terms of the evolution of the T and B immune systems.
Assuntos
Linfócitos B/imunologia , Bolsa de Fabricius/imunologia , Galinhas/imunologia , Genes de Imunoglobulinas , Imunoglobulinas/genética , Animais , Diversidade de Anticorpos , Bolsa de Fabricius/embriologia , Região Variável de Imunoglobulina/genéticaRESUMO
Transcriptional regulatory elements have been shown to be necessary but not sufficient for the developmental regulation of immunoglobulin gene rearrangement in mouse precursor B cells. In the chicken lambda light chain locus, additional elements in the V-J intervening sequence are involved in negative and positive regulation of rearrangement. Here, mutation of the mouse homolog of a chicken element, located in the V(K)-J(K) intervening sequence upstream of the J(K) cluster, was shown to significantly decrease rearrangement. This cis-acting recombination-enhancing element affects the rearrangement process without being involved in regulating transcription.
Assuntos
Rearranjo Gênico do Linfócito B , Genes de Imunoglobulinas , Cadeias J de Imunoglobulina/genética , Cadeias kappa de Imunoglobulina/genética , Sequências Reguladoras de Ácido Nucleico , Alelos , Animais , Linfócitos B/citologia , Linfócitos B/imunologia , Sequência de Bases , Quimera , Elementos Facilitadores Genéticos , Rearranjo Gênico do Linfócito T , Marcação de Genes , Região Variável de Imunoglobulina/genética , Íntrons , Camundongos , Camundongos Endogâmicos C57BL , Camundongos SCID , Dados de Sequência Molecular , Mutação , Recombinação Genética , Células-TroncoRESUMO
Studies of the immune system of various species have revealed that antibody repertoire can be generated in many different ways. This review underlines some general principles for comparing the different processes which represent the basic framework of these systems.
Assuntos
Linfócitos B/imunologia , Galinhas/imunologia , Coelhos/imunologia , Ovinos/imunologia , Animais , Linfócitos B/citologia , Medula Óssea/imunologia , Bolsa de Fabricius/imunologia , Diferenciação Celular/imunologia , Imunoglobulinas/imunologia , Nódulos Linfáticos Agregados/imunologiaRESUMO
We describe here two novel mouse and human DNA polymerases: one (pol lambda) has homology with DNA polymerase beta while the other one (pol mu) is closer to terminal deoxynucleotidyltransferase. However both have DNA polymerase activity in vitro and share similar structural organization, including a BRCT domain, helix-loop-helix DNA-binding motifs and polymerase X domain. mRNA expression of pol lambda is highest in testis and fetal liver, while expression of pol mu is more lymphoid, with highest expression both in thymus and tonsillar B cells. An unusually large number of splice variants is observed for the pol mu gene, most of which affect the polymerase domain. Expression of mRNA of both polymerases is down-regulated upon treatment by DNA damaging agents (UV light, gamma-rays or H(2)O(2)). This suggests that their biological function may differ from DNA translesion synthesis, for which several DNA polymerase activities have been recently described. Possible functions are discussed.
Assuntos
DNA Polimerase Dirigida por DNA/química , Processamento Alternativo , Sequência de Aminoácidos , Animais , Linhagem Celular , Clonagem Molecular , Dano ao DNA , DNA Polimerase beta/química , DNA Polimerase beta/classificação , DNA Complementar/isolamento & purificação , DNA Polimerase Dirigida por DNA/classificação , DNA Polimerase Dirigida por DNA/isolamento & purificação , Escherichia coli , Regulação Enzimológica da Expressão Gênica , Humanos , Camundongos , Dados de Sequência Molecular , Filogenia , Conformação Proteica , Estrutura Terciária de Proteína , Homologia de Sequência de Aminoácidos , Distribuição Tecidual , Células Tumorais CultivadasRESUMO
Transfection of the human CD4 molecule into mouse cells does not confer susceptibility to human immunodeficiency virus type 1 (HIV-1) infection. Expression of the human CD4 molecule in transgenic mice was seen to offer some new possibilities. However, transgenic mouse T cells expressing either the human CD4 receptor, or a hybrid human/mouse CD4 receptor alone or in conjunction with human major histocompatibility complex class I molecules, were refractory to in vitro HIV-1 infection. In addition, no infection was observed after in vivo HIV inoculation to mice of these various transgenic lines. Injection of recombinant gp160 viral protein to the transgenic mice did not alter their T and B cell populations. The existence of a dominant block in mouse cells that prevents HIV entry is discussed.