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P Leder

Publications and source records attributed to P Leder.

At least 217 records · Page 12Linked to original sources
PubMed1982

Translocation of the c-myc gene into the immunoglobulin heavy chain locus in human Burkitt lymphoma and murine plasmacytoma cells.

The consistent appearance of specific chromosomal translocations in human Burkitt lymphomas and murine plasmacytomas has suggested that these translocations might play a role in malignant transformation. Here we show that transformation of these cells is frequently accompanied by the somatic rearrangement of a cellular analogue of an avian retrovirus transforming gene, c-myc. Moreover, we map c-myc to human chromosome 8 band q24, the chromosomal segment involved in the reciprocal Burkitt translocations [t(8;14), t(8;22) and t(2;8)]. In two t(8;14) human Burkitt cell lines, c-myc appears to have been translocated directly into a DNA restriction fragment that also encodes the immunoglobulin mu chain gene. In the case of a specific cloned fragment of DNA derived from a mouse plasmacytoma, we demonstrate directly that c-myc has been translocated into the immunoglobulin alpha switch region. Our data provide a molecular basis for considering the role that specific translocations might play in malignant transformation.

Animals↗
PubMed1982

Globin genes: a paradigm of gene structure, function, and evolution.

Access to the detailed structure of the globin (and other) genes has taught us at least three valuable, but not necessarily expected, lessons regarding the structure and evolution of the genes. Foremost, at least in terms of its surprising nature, is the fact that many genes are interrupted, i.e., they contain discontinuous blocks of coding and noncoding information. No less surprising are the accompanying facts that chromosomal DNA changes by the movement and rearrangement of large pieces of DNA and that genetic loci are highly and unexpectedly complex, consisting of arrays of related genes and pseudo (or apparently nonfunctional) genes. Here we review some of the evidence upon which these conclusions rest, and we try to form a coherent picture of gene evolution. The evidence that we shall use is based on studies of the mouse globin. Evidence from various other genetic systems leads us to believe that these genes serve as an instructive general model rather than an idiosyncratic one.

Animals↗
PubMed1982

Moving genes.

We have seen that an essentially linear genome can amplify its genetic information by permitting the shuffling of widely separated genetic sequences. This shuffling can occur not only by the covalent joining of DNA, but also by alternative splicing of messenger RNA transcripts. While the mechanism is a required step in the development of an immunoglobulin producing cell, it is probably but one example of its action in the organism. It is difficult to imagine that an organism as complex as man can be created from an essentially linear array of nine billion nucleotides. The example provided by the immunoglobulin genes offers a mechanism for amplifying this genetic information. Our challenge is to find additional genetic systems that take advantage of these powerful mechanisms.

Animals↗
PubMed1981

Human immunoglobulin D segments encoded in tandem multigenic families.

A family of germ-line immunoglobulin D-region genes has been cloned and mapped at regular intervals along a 33-kilobase length of human chromosomal DNA. Each member of the family varies slightly in sequence, but precisely conserves the recombinational signals and spacing that flank each gene. This region seems to have been formed by the tandem amplification of large and still well conserved segments of genomic DNA. Further, structural comparisons of germ-line and rearranged D segments suggest that D segments may recombine with each other.

Antibody Diversity↗
PubMed1981

Clustered arrangement of immunoglobulin lambda constant region genes in man.

The immunoglobulin lambda light chain locus of man contains six lambda-like genes arranged tandemly on a 50-kilobase segment of chromosomal DNA. THe sequences of three of these genes correspond to three known non-allelic lambda chain isotypes: Mcg, Ke-Oz- and Ke-Oz+. They surround a highly polymorphic and evidently unstable region that is repeatedly deleted when cloned in Escherichia coli. Three additional, but as yet unlinked, lambda-like sequences have also been cloned, suggesting that the lambda genes form an unexpectedly large family within the human genome.

Base Sequence↗
PubMed1981

The nucleotide sequence of a 5.5-kilobase DNA segment containing the mouse kappa immunoglobulin J and C region genes.

We have determined the nucleotide sequence of a 5.5-kilobase segment of cloned mouse DNA which includes regions encoding two parts of the mouse kappa immunoglobulin gene: the J regions (amino acids 96-108 of the kappa chain) and the C region (residues 109-214). This sequence allows us to rule out interruptions in the germline constant region coding segment as well as the presence of additional functional J genes in the sequenced DNA segment, although two weak homologies to J regions have been found. The complete sequence also allows us to identify a single occurrence of the heptanucleotide palindrome thought to play a role in V/J joining. This palindrome, midway between J and C regions, is the site of aberrant joining in the plasmacytoma MPC11 and may be a target for such aberrant recombination of other kappa genes. In addition, computer analysis of the J sequences suggests that those closest to the C region arose by the most recent duplication event.

Animals↗
PubMed1981

Nucleic acid and protein sequences of phosphocholine-binding light chains.

An 18-kilobase DNA fragment containing the sequence coding for both the variable and constant regions of the S107 mouse immunoglobulin light chain was cloned from total cellular DNA. The complete nucleotide sequence of the kappa-chain variable-region gene is reported. Determination of the amino acid sequence encoded by the DNA is found to be identical to the protein sequence of the T15 light chain through residue 88. Direct sequence analysis confirmed that the J1 joining segment is used in the recombination event producing the active kappa light chain gene.

Amino Acid Sequence↗
PubMed1981

Human immunoglobulin kappa light-chain genes are deleted or rearranged in lambda-producing B cells.

We have examined 10 human lambda light-chain-producing B lymphocytes and found that genes for the kappa constant region have been deleted in each. Only one of the 20 possible kappa alleles in these cells has been retained and even this exception is rearranged. In contrast, lambda constant region genes remain in the germ-line configuration in each of the eight kappa light-chain-producing human B lymphocytes examined. Such observations suggest a hierarchy of light-chain-gene rearrangement beginning with kappa and proceeding to lambda.

Alleles↗
PubMed1981

Two kappa immunoglobulin genes are expressed in the myeloma S107.

We have cloned two rearranged kappa immunoglobulin genes from the mouse myeloma cell line S107, and find that both are expressed. One gene, designated S107A, encodes the secreted kappa chain that participates in phosphocholine binding and expression of the T-15 idiotype. The other gene, designated S107B, as described here, contains an unusual junction between a V region unrelated to that of S107A and a different J region. The V-J junction preserves the triplet reading frame, but 6 nucleotides have been deleted at the recombination site. Nucleotide sequence analysis of the germline V-region precursor of S107B in comparison with other germline kappa-variable sequences reveals an "extra" 2 nucleotides in S107B between codon 95 and the palindromic heptanucleotide CACAGTG previously implicated in V-J recombination; this difference may be relevant to the 6 nucleotide deletion. Both S107A and S107B genes are expressed in the S107 cell as protein products, but unlike the S107A kappa chain, the S107B protein product is not secreted into the medium. The expression of these two kappa genes in the S107 cell has implications for theories of allelic exclusion.

Alleles↗
PubMed1981

Structure of the human immunoglobulin mu locus: characterization of embryonic and rearranged J and D genes.

The variable portion of an immunoglobulin heavy chain gene is assembled from at least three discontinuous segments of DNA, the V, D and J regions. We have characterized a 30 kb segment of the human genome that plays a critical role in the formation of this variable region as well as in the expression of the two heavy chains that appear earliest in immunocyte ontogeny, the mu and delta chains. This region encodes nine J-like segments, an interspersed D segment, recombination signals and the genes responsible for the production of both mu and delta heavy chains. Six of the nine germline J-like genes appear to be active and easily account for most of the known human heavy chain amino acid sequences. Three of the J-like genes are pseudogenes. The large number of human J region genes and, hence, their greater potential for generating diversity as compared to the that of the mouse J region genes appears to result from recent genetic duplications. To assess this potential, we have analyzed two recombinant genes involving this region. One of these, a V-D-J recombinant, is likely to be an active gene; the other, an aberrant D-J recombinant. A comparison of the structures of these D regions raises the possibility that they are mosaics formed by recombination between D segments.

Amino Acid Sequence↗
PubMed1981

Developmental hierarchy of immunoglobulin gene rearrangements in human leukemic pre-B-cells.

We have used a special class of human acute lymphocytic leukemias, the common "non-T/non-B" cell type, to define a hierarchy of genetic rearrangements that occur during the earliest stages of B-cell maturation. This has allowed us to identify intermediate cells predicted by a hierarchial model in which immunoglobulin heavy chain variable region gene formation precedes that of light chain and in which kappa light chain gene formation precedes that of lambda. The model emphasizes the flexible nature of immunoglobulin gene recombination that not infrequently produces aberrant or null genes that are phenotypically excluded from expression. Remaining alleles or isotypic genes can then be utilized as "spares" undergoing recombination until a valid gene is formed. Significantly, the excluded allele or isotype is frequently deleted from the genome. In addition to defining a pathway of genetic maturation, this analysis provides a powerful means to further classify cases of non-T/non-B-cell acute lymphocytic leukemia, most of which seem to reside at early stages along the B-cell pathway of differentiation.

DNA Restriction Enzymes↗
PubMed1981

Recombination events that activate, diversify, and delete immunoglobulin genes.

Immunoglobulin kappa light-chain diversity arises, in large part, from an array of germ-line V-region genes that undergo somatic recombination with one of four active J-region segments. The diversity provided by this combinational system is increased by a recombination mechanism that allows variation of crossover points so as to generate additional diversity at a critical region of the light chain. The elaborate mechanism for generating diversity is accompanied not only by considerable waste, in terms of unused V and J regions in a given cell, but also by a range of aberrant recombinants that fail to produce active immunoglobulin genes.

Animals↗
PubMed1981

The organization and evolution of cloned globin genes.

The globin genes represent a complex set of sequences that are expressed in a coordinate fashion during the development of red blood cells. while this complex family of genes may consist of as many as ten to fourteen members [34], three of these genes have now been cloned and their entire nucleotide sequence determined. As was initially observed in the case of beta globin major gene, all are encoded in three distinct coding blocks separated by two intervening sequences of DNA. Their intervening sequences of DNA are preserved, with respect to location, but are widely divergent, with respect to size and sequence. The divided information in each gene is edited and spliced together at the level of its initial RNA transcript which is complementary to the entire gene sequence including its intervening sequences. Structural correlation analyses have allowed us to identify sites in all three genes that might be responsible for the initiation of transcription, RNA splicing, and poly A addition. The function of these sites has been tested by cloning these genes in an animal virus vector SV40. Such animal virus hybrids have been used to infect tissue culture cells and have directed the synthesis of both alpha and beta mouse globin in cells of monkey origin. These studies indicate that such signals operate across species barriers and further indicate that the animal virus vector system will be useful in elucidating their function.

Amino Acid Sequence↗
PubMed1980

Mouse globin system: a functional and evolutionary analysis.

Structural and functional analysis of the mouse alpha-globin and beta-globin genes reveals that the globin genes are encoded in discontinous bits of coding information and that each gene locus is much more complex than was originally supposed. Each seems to consist of an array of several authentic genes as well as several apparently inactive pseudogenes. Comparison of the sequences of some of these genes to one another indicates that chromosomal DNA is a dynamic structure. Flanking and intervening sequences change in two ways: quickly, by duplication and extensive insertions and deletions, and slowly, by point mutation. Active coding sequences are usually limited to the slower mode of evolution. In addition to identifying fast and slow modes of evolution, it has also been possible to test the function of several signals that surround these genes and to identify those that appear to play a role in gene expression.

Animals↗
PubMed1980

A mutant immunoglobulin light chain is formed by aberrant DNA- and RNA-splicing events.

A mutant immunoglobulin gene has been formed by an abnormal (non V/J) recombination event such that abnormal RNA splicing is required to form a mutant light chain. The structure of the gene suggests that the small palindrome thought to be involved in V/J joining also provides the basis for this abnormal DNA recombination and that the absence of a J segment and RNA splice signal allows an abnormal RNA splicing reaction to occur.

Alleles↗
PubMed1980

Organization and complete sequence of identical embryonic and plasmacytoma kappa V-region genes.

We have determined the entire sequence of two immunoglobulin kappa variable region genes derived separately from embryonic and plasmacytoma cells. Both genes are in the germline configuration; both are organized into hydrophobic leader and mature V-region coding sequences separated by a short intervening sequence. Both are identical with one another throughout the 1360 bases determined. In addition, there is a simple repeat sequence of 31 CA doublets that occurs about 300 bases from the 3' side of the coding sequence in each gene.

Amino Acid Sequence↗
PubMed1980

Cloned human and mouse kappa immunoglobulin constant and J region genes conserve homology in functional segments.

The human immune system offers special advantages for study of the development and evolution of the immune response. A variety of human cell lines are available that are arrested at various stages of development, and human genes provide a convenient evolutionary point of comparison with the already well characterized genes of the mouse. In this paper, we describe the procedure we have used to clone the human kappa chain genes in both germline and rearranged configurations. We have taken advantage of distantly related probes derived from the mouse and nonstringent conditions of hybridization to find the human genes among phage lambda recombinants formed with partially purified genomic restriction fragments of human DNA. In addition to establishing a physical map of the human kappa C and J regions, we have determined the entire sequence of a germline human constant region gene (the Inv3 allele) and two of its J segments, as well as the V/J recombination site of an active human kappa chain gene. For purposes of comparison, we also determined the sequence of the chromosomal mouse constant region gene and its flanking sequences. Although mouse and human sequences have changed extensively during the 70 million years since the two species diverged. significant blocks of homology have been conserved selectively. Some of these have obvious significance in terms of DNA and RNA splicing reactions. By forming heteroduplex structures between mouse and human genes we were able to identify four human J regions that are much more stringently conserved throughout their coding sequences than are the C region genes. In addition, the middle j structure (J3) of the mouse (which is thought to be inactive) appears to be missing from the human genome.

Animals↗