Recombined flanks of the variable and joining segments of immunoglobulin genes.

Abstract

The mechanism of generating immunoglobulin light chain genes by rearrangement ofvariable (V), joining (J), and constant (C) gene segments is still unknown. It has been discussed mostly in terms of excision and deletion of the DNA between the recombined V and J gene segments. However, the finding in DNA digests from the mouse myeloma T of a fragment (called f-T) that contains the 3' flank of a VK and the 5' flank of a JI gene segment argued against a simple deletion mechanism ) Nucleic Acids Res. 8, 1709-1720. The origin of fragment f-T has now been investigated by cloning and determining the sequence of the germ-line V gene segment that apparently participated in its formation. Moreover, analogous fragments containing flanking sequences were isolated from the myelomas MOPC 173 and 41 (f-173 and f-41) and studied by sequence analysis. The ffragments appear to be recombination products ofV-J rearrangements reciprocal to rearranged X genes but, at least in the cases of f-T and f-173, not of the rearranged V genes present in the same tumor cell. This fact is best explained by a sister chromatid exchange mechanism of V-J recombination because, by this model, the rearranged V genes and the reciprocal flank recombination products would segregate into different cells during the following mitosis. The possibility is suggested that there exists in lymphocyte differentiation more than one mechanism of V-J recombination. The genes for the immunoglobulin light chains are generated by recombination of a variable (V) with a joining (J) gene segment that is located near the constant (C) gene region (1-3). In the K light chain system of the mouse, one of many V gene segments is joined to one offour functional J gene segments (2-4). In addition to functional V-J rearrangements, nonfunctional ones have been observed (5-8) that, at least in some cases, result from aberrations at the V-J junction (5-7). The functional and nonfunctional genes have been termed K+ and K-, respectively (4).One of the unsolved problems in the generation of immunoglobulin genes is the mechanism of V-J joining. Hybridization experiments with DNA from a A (1, 3) and a K chain producing tumor (2, 9) indicated that the sequences 3' adjacent to the rearranging germ-line V gene segment and 5' adjacent to the respective J gene segment (3' V and 5' J flanks) are deleted in the V-J recombination process. These results and the identification of complementary hepta-and nonanucleotide boxes in the 3' flanks of V gene segments and the 5' flanks of J gene segments led to the proposal of hybrid stem structures that are excised and deleted (2, 3). Schemes have also been formulated that do not involve pairing of DNA single strands but rather recognition of the original double-stranded regions by a recombining enzyme and subsequent deletion of the DNA between the V and J gene segments (10, 11).One argument against a simple excision-deletion model was the finding, in myeloma T (5, 12) DNA digests, of a fragment in which the 3' flank of a V gene was linked directly...

Nonproductive kappa immunoglobulin genes: recombinational abnormalities and other lesions affecting transcription, RNA processing, turnover, and translation.

“…It is important to note that our observation is not inconsistent with the results predicted by other recombination models based on interchromatid exchange (19,55) or episomal reinsertion (50). However, a particularly attractive feature of the intrachromatid recombination model described above is the manner in which the initial orientation of the recombination signals unequivocally predicts the fate of the recombination products.…”

“…In normal VK-JK fusion, these signals are always removed from the recombinational joint and are either lost from the genome or displaced to another chromosomal site; in D-JH and VH-D recombinations of heavy-chain genes, they are invariably lost from the genome (2,55). In all of the displaced K signals characterized to date, the heptamers are precisely fused, just as they are in the PC 8701 and PC 10916 K-alleles (19).…”

“…Secondary recombinations that generate new reciprocal joints and delete the original ones (Fig. 13e) could account for the frequent lack of a reciprocal relationship between the retained fused heptameric structure and the VK-JK joint (19,28,50,55).…”

Joining of immunoglobulin heavy chain gene segments: implications from a chromosome with evidence of three D-JH fusions.

“…2). Similarly, perfectly fused VK and JK recognition sequences are often found as reciprocal joining fragments in cells that have undergone VK-to-JK joining (17,18). Again, however, the VK-to-JK joining is almost never precise (2,3,14).…”

Preferential rearrangement of the immunoglobulin kappa chain joining region J kappa 1 and J kappa 2 segments in mouse spleen DNA.

“…The immunoglobulin variable (V) region repertoire is determined by the number of germ-line segments encoding the V region and by the efficiency of somatic genetic events that amplify germ-line diversity (1)(2)(3) (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) MATERIALS AND METHODS Materials. BALB/c strain mice were used unless otherwise specified.…”