Coordinate Transcription and V(D)J Recombination of the Kappa Immunoglobulin Light-Chain Locus: NF-κB-Dependent and -Independent Pathways of Activation

Abstract

To further elucidate the potential role of mitogens and cytokines in regulation of the kappa immunoglobulin light-chain locus, we have characterized the activation of transcription factor binding, kappa germ line transcription, DNase I hypersensitivity, and V -to-J recombination upon induction of model pre-B-cell lines. We find that both lipopolysaccharide (LPS) and gamma interferon (IFN-␥) are capable of activating germ line transcription, DNase I hypersensitivity, and recombination of the kappa locus. We also find that transforming growth factor ␤ is capable of completely inhibiting LPS activation of transcription and recombination but has no apparent effect on activation of transcription factor binding, It is becoming increasingly clear that the tissue-specific and developmentally regulated transcription and recombination of immunoglobulin (Ig) gene segments represent overlapping points of control during B-cell development. The concomitant activation of transcription and recombination of all Ig loci has led to the suggestion that transcription of unrearranged Ig genes plays a key role in regulating recombination (23, 31, 37, 44-46, 55, 60, 61). A number of observations have provided strong support for this hypothesis. First, while a common V(D)J recombinase is expressed in both B cells and T cells, functional recombination of Ig genes is restricted to B cells, where they are also transcriptionally active (62). While ectopic expression of the recombinase activating genes RAG-1 and RAG-2 has been shown to confer V(D)J recombinase activity to integrated and extrachromosomal substrates in nonlymphoid cells, the endogenous Ig loci, which are transcriptionally silent in these cells, do not undergo recombination (19,25,33). In addition, it has been demonstrated previously that induction of germ line transcription of the unrearranged kappa Ig lightchain and heavy-chain loci is accompanied by an increased frequency of gene rearrangement (44, 45). More direct evidence that cis-acting transcriptional regulatory elements are involved in recombination has been demonstrated by integration of recombination substrates by using transfection approaches (5, 6, 11, 24, 35), transgenic approaches (15-17, 20, 21), and targeted knockouts of endogenous sequences (18,48,54,59).While there is strong evidence that cis-acting transcriptional regulatory regions within the kappa Ig light-chain locus play a role in recombination, the mechanism by which they regulate recombination and the trans-acting factors involved have yet to be elucidated. The observation that cells are able to regulate the ability of the endogenous kappa locus to serve as a substrate for the V(D)J recombinase has led to the suggestion that transcription may target the locus by providing accessibility of the locus to the recombinase (see reviews in references 32, 39, and 47). The mechanism by which transcription may mediate accessibility is not clear; however, changes in local chromatin structure within the kappa locus have been shown to occur upon transcriptional ac...

Induction of differentiation of pre-NKT cells to mature Vα14 NKT cells by granulocyte/macrophage colony-stimulating factor

“…In some pre-B cell lines, certain humoral factors, such as bacterial lipopolysaccharide and interferon ␥, are demonstrated to induce germ-line transcription and rearrangement of Ig locus by converting the inactive Ig locus to an accessible recombinase substrate (24,25). Similarly, germline transcripts of J␥-C␥ appear to be induced by IL-3, implying that IL-3 allowed the TCR␥ loci to open (26).…”

Dynamic Changes in Accessibility, Nuclear Positioning, Recombination, and Transcription at the Igκ Locus

“…For rag2, ␤-actin, and °transcripts, the cycling parameters were identical to those above except that the annealing temperature was 62°C. The RT-PCR primers used in this study have been previously described (15,16) The primer sets for rag1, rag2, 5, and Vpre-B were designed to amplify across introns (15). In the case of °transcripts, only spliced products (17) were detected.…”

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