Transposed human immunoglobulin V kappa gene regions carry clusters of conserved sequence elements.

The V kappa I gene regions which have been transposed in evolution from the site of the kappa locus on chromosome 2 to chromosomes 1, 22, and other chromosomes, are very similar and may have been derived from one ancestor gene. Upstream from the transposed genes (called orphons) two types of conserved sequence elements were found using a mouse cell assay system. One type is homologous to the murine sequences which were previously thought to be ARS elements; the other one is related to the binding site of the replication/transcription factor NFIII. Such a combination of elements was seen neither in hybridization experiments with the 1 Mb of the kappa locus available on cosmid clones nor in a computer-aided search of sequence data libraries. We speculate that in the evolutionary past, the clustered elements played a role in the transposition of the V kappa genes, perhaps by causing an over-replication and/or by facilitating the integration of the genes.

Localization, analysis and evolution of transposed human immunoglobulin V kappa genes.

The localization of V kappa gene regions to chromosome 2, on which the kappa locus is located, and to other chromosomes is described. The V kappa genes that have been transposed to other chromosomes are called orphons. The finding of two new V kappa genes on chromosome 22 is reported. A V kappa II gene of this region and two V kappa I genes of the Chr1 and the cos 118 regions were sequenced. The two V kappa I orphon sequences and two others that had been determined previously were 97.5% identical, indicating that they may have evolved from a common ancestor by amplification. A model of the evolution of the human V kappa orphons is discussed.

A signal regulating mouse histone H4 mRNA levels in a mammalian cell cycle mutant and sequences controlling RNA 3' processing are both contained within the same 80-bp fragment.

Fragments from the 3' end of a mouse histone H4 gene, when introduced into transcription units controlled by the SV40 early promoter, yield correctly processed RNA with histone-specific 3' ends, both in monkey and mouse cell lines. The processed RNA is regulated in parallel with endogenous H4 mRNAs in 21-Tb cells, a temperature-sensitive mouse mastocytoma cell cycle mutant that is specifically blocked in G1 phase at the non-permissive temperature. Mutational analyses of the H4 gene fragment indicate that the minimal sequences for this regulation and for RNA 3' processing are both contained within the same 80 bp. This fragment contains two histone-specific, highly conserved sequence elements that are located at the 3' end of histone mRNA and in the adjacent spacer region, respectively. Our data suggest that the observed cell cycle regulation is achieved either at RNA 3' processing or at some later step involving the conserved 3'-terminal sequence element of mature histone mRNA.

A human immunoglobulin kappa orphon without sequence defects may be the product of a pericentric inversion.

The VK gene segments that have been transposed from the kappa locus on the short arm of chromosome 2 at 2p11-12 to other chromosomal sites are called orphons. The 18 VK orphons sequenced up to now carry defects and are to be considered pseudogenes. We now describe the VKI gene segment V108 whose sequence is without any defects and which was localized to the long arm of chromosome 2 at 2q12-14 by in situ hybridization. The V108 region may have been transposed from the short to the long arm of chromosome 2 by a pericentric inversion. Possible reasons for the conservation of its sequence are discussed. In spite of its bona fide sequence V108 is considered to be an unlikely candidate for a VK-JK rearrangement and subsequent functional expression.

Bispecific antibodies that mediate killing of cells infected with human immunodeficiency virus of any strain.

Although AIDS patients lose human immunodeficiency virus (HIV)-specific cytotoxic T cells, their remaining CD8-positive T lymphocytes maintain cytotoxic function. To exploit this fact we have constructed bispecific antibodies that direct cytotoxic T lymphocytes of any specificity to cells that express gp120 of HIV. These bispecific antibodies comprise one heavy/light chain pair from an antibody to CD3, linked to a heavy chain whose variable region has been replaced with sequences from CD4 plus a second light chain. CD3 is part of the antigen receptor on T cells and is responsible for signal transduction. In the presence of these bispecific antibodies, T cells of irrelevant specificity effectively lyse HIV-infected cells in vitro.

Dispersed human immunoglobulin kappa light-chain genes.

The gene segments encoding the constant and variable regions of human immunoglobulin light chains of the kappa type (C kappa, V kappa) have been localized to chromosome 2. The distance between the C kappa and V kappa genes and the number of germline V kappa genes are unknown. As part of our work on the human V kappa locus, we have now mapped two solitary V kappa gene and a cluster of three V kappa genes to chromosomes 1, 15 and 22, respectively. The three genes that have been sequenced are nonprocessed pseudogenes, and the same may be true for the other two genes. This is the first time that V-gene segments have been found outside the C-gene-containing chromosomes. Our finding is relevant to current estimates of the size of the V kappa-gene repertoire. Furthermore, the dispersed gene regions have some unusual characteristics which may help to clarify the mechanism of dispersion.