Structure and expression of germ line immunoglobulin gamma 2b transcripts.

Lutzker, Stuart; Alt, Frederick W.

doi:10.1128/mcb.8.4.1849

Cited by 126 publications

(76 citation statements)

References 16 publications

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“…Moreover, recent genetic knockout experiments show that regulatory sequences must function in cis to stimulate switch recombination in activated B lymphocytes (16,42 Our data show that recombinational stimulation in the switch substrates does require protein binding to the regulatory element, but recombination appears to be independent of transcript production. A temporal correlation between recombination and transcriptional activation has been documented both for isotypes switching and for V(D)J joining in mammalian lymphocytes, and Alt and coworkers have suggested that transcription could regulate recombination by rendering a region of DNA accessible to factors or lesions that promote recombination (3,5,21,39). However, there is considerable recent data suggesting that transcript production and recombination may not be mechanistically linked in mammalian cells.…”

Section: Discussionmentioning

confidence: 94%

Regulation and targeting of recombination in extrachromosomal substrates carrying immunoglobulin switch region sequences.

Leung¹,

Maizels²

1994

Mol. Cell. Biol.

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We have used extrachromosomal substrates carrying immunoglobulin heavy-chain S,u and Sy3 switch region sequences to study activation and targeting of recombination by a transcriptional enhancer element. Substrates are transiently introduced into activated primary murine B cells, in which recombination involving S-region sequences deletes a conditionally lethal marker, and recombination is measured by transformation of Escherichia coli in the second step of the assay. Previously we found that as many as 25% of replicated substrates recombined during 40-h transfection of lipopolysaccharide (LPS)-stimulated primary cells and that efficient recombination was dependent on the presence of S-region sequences as well as a transcriptional activator region in the constructs (H. Leung and N. Maizels, Proc. Natl. Acad. Sci. USA 89:4154-4158, 1992). Here we show that recombination of the switch substrates is threefold more efficient in LPS-cultured primary B cells than in the T-cell line EL4; the activities responsible for switch substrate recombination thus appear to be more abundant or more active in cells which can carry out chromosomal switch recombination. We test the role of the transcriptional activator region and show that the immunoglobulin heavy-chain intron enhancer (E,u) alone stimulates recombination as well as E,L combined with a heavy-chain promoter and that mutations that diminish enhancer-dependent transcription 500-fold diminish recombinational activation less than 2-fold. These observations suggest that the enhancer stimulates recombination by a mechanism that does not depend on transcript production or that is insensitive to the level of transcript production over a very broad range.Furthermore, we find that E,u stimulates recombination when located either upstream or downstream of SFL but that the position of the recombinational activator does affect the targeting of recombination junctions, suggesting that the relatively imprecise targeting of switch junctions in vivo may reflect the availability of many potential activator sites within each switch region.Immunoglobulin isotype switch recombination is a regulated recombination event which joins an expressed heavychain variable [V(D)J] region to a new downstream constant (C) region, deleting the DNA between (for reviews, see references 5, 6, and 8). Isotype switching occurs in B cells which have accomplished V(D)J joining and have been activated by antigen. Recombination involves G-rich switch or S regions, from 1 to 8 kb in length, which are found in the intron upstream of each C region that undergoes switching-C,u, Cy, Ca, and Ce; expression of Ca is regulated by alternative splicing, not recombination, and there is no G-rich S region upstream of Ca. In contrast to V(D)J joining, in which heptamer-nonamer recognition elements precisely target recombination (13), switch recombination is notably imprecise. No conserved sequences comparable to the heptamer-nonamer elements are apparent within S regions or at switch recombination sites, and chromosomal swi...

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Section: Discussionmentioning

confidence: 94%

Regulation and targeting of recombination in extrachromosomal substrates carrying immunoglobulin switch region sequences.

Leung¹,

Maizels²

1994

Mol. Cell. Biol.

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“…In response to stimulation of mature B cells by interleukins and/or other T-cell-or macrophageproduced factors, nuclear proteins (73) would bind to the tandem repeat area of the ,u locus. In response to other interleukins and other factors, the second portion of the switch complex would form near a downstream tandem repeat (switch) region (68), perhaps after the region is made accessible due to germ line (sterile) transcription (32,36,53 (20). The IgH locus inversions and duplications that are attributed to sister chromatid exchange might also be mediated by this mechanism, since switch complexes can assemble on the C of one chromosome and on a CH on another chromosome (16).…”

Section: Discussionmentioning

confidence: 99%

Nonhomologous recombination at sites within the mouse JH-C delta locus accompanies C mu deletion and switch to immunoglobulin D secretion.

Owens¹,

Finkelman²,

Mountz³

et al. 1991

Mol. Cell. Biol.

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Plasma cells secrete immunoglobulins other than immunoglobulin M (IgM) after a deletion and recombination in which a portion of the immunoglobulin heavy-chain locus (IgH), from the 5'-flanking region of the ,u constant-region gene (C,e) to the 5'-flanking region of the secreted heavy-chain constant-region gene (CH), is deleted. The recombination step is believed to be targeted via switch regions, stretches of repetitive DNA which lie in the 5' flank of all CH genes except 8. Although serum levels of IgD are very low, particularly in the mouse, IgD-secreting plasmacytomas of BALB/c and C57BL/6 mice are known. In an earlier study of two BALB/c IgD-secreting hybridomas, we reported that both had deleted the C,, gene, and we concluded that this deletion was common in the normal generation of IgD-secreting cells. To learn how such switch recombinations occur in the absence of a switch region upstream of the Cr,1 exon, we isolated seven more BALB/c and two C57BL/6IgD-secreting hybridomas. We determined the DNA sequences of the switch recombination junctions in eight of these hybridomas as well as that of the C57BL/6 hybridoma B1-8.81 and of the BALB/c, IgD-secreting plasmacytoma TEPC 1033. All of the lines had deleted the C, gene, and three had deleted the C,,, exon in the switch recombination event. The delta switch recombination junction sequences were similar to those of published productive switch recombinations occurring 5' to other heavy-chain genes, suggesting that nonhomologous, illegitimate recombination is utilized whenever the heavy-chain switch region is involved in recombination. The switch from ,u, the 5'-most heavy-chain constantregion gene, to other heavy-chain classes is accomplished by another somatic rearrangement of the heavy-chain locus, the switch recombination. In switch recombination, a 5' breakpoint upstream of the C,, gene is joined to a 3' breakpoint upstream of another CH gene, and the intervening DNA is deleted. The switch recombination has been linked to switch regions: 2 to 5 kb of tandem repeats in which the tetramers AGCT and TGGG occur frequently (46). Switch regions are found in the 5'-flanking area of each CH gene except C6. Curiously, most switch recombinations do not have their 5' breakpoints in the switch ,u region (S,,), though the 3' breakpoints usually are in the switch region of the expressed CH gene (25). Since IgD is rare in human serum and very rare in mouse serum, it was believed that normal production of secreted * Corresponding author. Synthesis of immunoglobulin (IgIgD might not require switch recombination but might occur by alternative splicing of transcripts spanning the VH-D-JH and C -C. locus, the same mechanism utilized for membrane IgD (reviewed in reference 6). Although human B cells with intact C,, genes can synthesize small but significant amounts of mRNA for secreted 8 chain (30), this is not the case in mice (15). It is likely that secretion of large amounts of IgD requires some sort of recombination, since three cultured human cell lines and three human m...

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“…Understanding the mechanisms governing the IgH locus, a model system for gene expression and epigenetic regulation will also advance our understanding of various other unsolved biological problems. (Chaudhuri et al, 2007;Lennon and Perry, 1985;Lutzker and Alt, 1988), only μ and γ1 I promoters (IμP, Iγ1P) are depicted. Transcripts from I promoters get spliced and polyadenylated.…”

Section: Discussionmentioning

confidence: 99%

“…I promoters are located upstream of all switch regions (Chaudhuri et al, 2007;Lennon and Perry, 1985;Lutzker and Alt, 1988). Transcripts initiating from I promoters are processed in such a way that an I (intervening) exon, located immediately downstream of the I promoter, is spliced to the associated C H exons.…”

Section: ′ Igh Regulatory Region and I Promotersmentioning

confidence: 99%

Chapter 1 Cis‐Regulatory Elements and Epigenetic Changes Control Genomic Rearrangements of the IgH Locus

Perlot

Alt

2008

Advances in Immunology

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Immunoglobulin variable region exons are assembled from discontinuous variable (V), diversity (D), and joining (J) segments by the process of V(D)J recombination. V(D)J rearrangements of the immunoglobulin heavy chain (IgH) locus are tightly controlled in a tissue-specific, ordered and allele-specific manner by regulating accessibility of V, D, and J segments to the recombination activating gene proteins which are the specific components of the V(D)J recombinase. In this review we discuss recent advances and established models brought forward to explain the mechanisms underlying accessibility control of V(D)J recombination, including research on germline transcripts, spatial organization, and chromatin modifications of the immunoglobulin heavy chain (IgH) locus. Furthermore, we review the functions of well-described and potential new cis-regulatory elements with regard to processes such as V(D)J recombination, allelic exclusion, and IgH class switch recombination.

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Structure and expression of germ line immunoglobulin gamma 2b transcripts.

Cited by 126 publications

References 16 publications

Regulation and targeting of recombination in extrachromosomal substrates carrying immunoglobulin switch region sequences.

Regulation and targeting of recombination in extrachromosomal substrates carrying immunoglobulin switch region sequences.

Nonhomologous recombination at sites within the mouse JH-C delta locus accompanies C mu deletion and switch to immunoglobulin D secretion.

Chapter 1 Cis‐Regulatory Elements and Epigenetic Changes Control Genomic Rearrangements of the IgH Locus

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