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U Storb

Publications and source records attributed to U Storb.

At least 73 records · Page 4Linked to original sources
PubMed1981

Rearranged and germline immunoglobulin kappa genes: different states of DNase I sensitivity of constant kappa genes in immunocompetent and nonimmune cells.

The rearrangement of a variable (V) and a constant (C) gene appears to be a necessary prerequisite for immunoglobulin gene expression. Multiple different rearranged kappa genes were found in several mouse myelomas, although these cells produce only one type of kappa chain [Wilson, R., Miller, J., & Storb, U. (1979) Biochemistry 18, 5013--5021]. It is therefore of interest to understand how only one allele within a lymphoid cell becomes expressed, while the other allele remains nonfunctional ("allelic exclusion"). We have studied the chromatin conformation of kappa genes by making use of the preferential digestion of potentially active genes by DNase I described, for example, for globin genes [Weintraub, H., & Groudine, M. (1976) Science (Washington, D.C.) 193, 848--856]. The DNase I sensitivity of kappa genes in myeloma tumors, in a B cell lymphoma, and in liver was determined by hybridization with DNA on Southern blots. It was found that rearranged C kappa genes are DNase I sensitive in myelomas in which several kappa genes are rearranged, regardless of whether the rearranged genes code for the kappa chains synthesized by the cell. Furthermore, the C kappa gene in germline configuration is also DNase I sensitive in a B cell lymphoma; i.e., it is in the same chromatin state as the rearranged C kappa gene which probably codes for the kappa chains produced by the cell. The altered chromatin state appears to be localized: V kappa genes in germline context are not DNase I sensitive in myeloma or B lymphoma cells while C kappa genes present in a kappa gene cluster on the same chromosomes are sensitive. When rearranged, however, the V kappa genes are as sensitive to DNase I as are rearranged C kappa genes. V lambda and C lambda genes are not DNase I sensitive in kappa myelomas. Thus, commitment to kappa gene expression is apparently correlated with a chromatin conformation which confers increased DNase I sensitivity to the DNA in the vicinity of all C kappa genes in the cell. "Allelic exclusion" does not operate on the level of chromatin conformation which can be detected by altered DNase I sensitivity.

Animals↗
PubMed1981

Somatic mutation of immunoglobulin light-chain variable-region genes.

A single germline immunoglobulin kappa-variable-region gene, VK167, is rearranged and expressed in two myelomas, MOPC167 and MOPC511. Only this single germline gene displays close homology to the expressed genes. Neither of the rearranged, functional genes, however, has a nucleotide sequence that is identical to the germline VK167 gene. Both active genes display several single-base-pair mutations with respect to the germline sequence. The nucleotide sequence data predict the alteration of a restriction-enzyme-recognition site within the VK167 gene between germline cells and cells producing the MOPC167 light-chain protein. Based on this restriction-site alteration, Southern blot analysis proves unambiguously that no gene present in the germline BALB/c mouse genome contains the exact VK167 nucleotide sequence found in cells committed to MOPC167 antibody production. Instead the alterations found in the expressed MOPC167 and MOPC511 V-region genes have apparently arisen by a process of somatic mutation during cellular differentiation. Since nucleotide alterations are found in framework and hypervariable portions of the variable region, the mechanism of somatic mutation is not limited to hypervariable sequences. In addition, Southern blot hybridization indicates that the observed mutations did not arise by recombinational events, but are single-base-pair substitutions. Based on the distribution of mutations that have been found in expressed immunoglobulin variable-region genes, a model that links the introduction of somatic mutations to DNA replication during the V-J joining event is proposed.

Amino Acid Sequence↗
PubMed1981

Physical linkage of the constant region genes for immunoglobulins lambda I and lambda III.

During differentiation from a stem cell to an antibody-secreting cell, the immunoglobulin genes within a B cell undergo a rearrangement that juxtaposes a variable region gene to a constant region gene. To analyze the genetic organization of an immunoglobulin gene family in nonrearranged, germ-line DNA, we have constructed a recombinant DNA library from randomly cleaved mouse kidney DNA fragments. From this library, we have isolated three overlapping recombinant clones containing the constant region gene for lambda I light chains (C lambda I). These clones spanned 24.9 kilobases of mouse DNA and contained no variable region sequences. Hybridization of these clones with lambda II cDNA demonstrated the presence of an additional constant region gene and a joining region 3.2 kilobases 5' of C lambda I. This gene was tentatively identified as C lambda III by the absence of an Ava I endonuclease site, which is present within C lambda II. The C lambda III amino acid sequence has recently been reported [Azuma, T., Steiner, L. A. & Eisen, H. N. (1981) Proc. Natl. Acad. Sci. USA 78, 569-573] and is very closely related to the C lambda II amino acid sequence.

Animals↗
PubMed1980

Myeloma with multiple rearranged immunoglobulin kappa genes: only one kappa gene codes for kappa chains.

In many myelomas more than one kappa gene is rearranged (2-5). We are reporting here the results of studies undertaken to determine whether all the rearranged genes are expressed. It was found that in the myeloma NS-1 three different rearranged kappa genes exist. In a subline of NS-1 and several hybridomas produced by fusion of mouse spleen cells with NS-1 it was found that production of NS-1 kappa chains was correlated with the presence of one of the three kappa genes. Loss of this "expressed" gene eliminated the synthesis of the NS-1 kappa chains, loss of one of the other two rearranged kappa genes did not. It is hypothesized, that allelic exclusion (20) of kappa genes generally operates by the functional rearrangement of one kappa gene; other rearrangements are relatively frequent, at least in myelomas, but mostly they are nonfunctional and thus scrambled antibody molecules do not arise.

Animals↗
PubMed1980

Comparison of different rearranged immunoglobulin kappa genes of a myeloma by electronmicroscopy and restriction mapping of cloned DNA: implications for "allelic exclusion".

We have studied the organization and function of different rearranged kappa genes in a myeloma, MOPC-21. Two kappa genes were cloned into Charon 4A and compared with each other and with a cloned germline CK gene by restriction mapping and electron microscopy. One MOPC-21 clone corresponds to the gene coding for the MOPC-21 kappa chain polypeptide; it has the V21 gene joined with the CK gene at the J2 sequence. The other MOPC-21 clone corresponds to a nonfunctional rearranged MOPC-21 kappa gene, except for a lkb deletion, 3' of J4. A similar deletion is also found in a "new" kappa gene present in NS-1, a cellular subclone of MOPC-21. The clone of the "nonfunctional" kappa gene has a V gene which is distinct from V21 which is joined to CK in the vicinity of J2. The undeleted form of this gene codes for a KRNA having the size of mature KmRNA which, however, is not translated into kappa chains. Thus the defect of the "nonfunctional" gene manifests itself at a late step of gene expression. The basis for "allelic exclusion" of antibody genes may simply be the complexity of the processes between genes and gene products, resulting in the expression of only one gene.

Alleles↗
PubMed1978

Immunoglobulin genes in DNA restriction fragments.

We have investigated the organization of immunoglobulin genes in mice. High molecular weight DNA from myelomas and Krebs ascites cells was cleaved with EcoRI restriction endonuclease and fractionated using preparative agarose gel electrophoresis. Each fraction was then hybridized to an immunoglobulin mRNA or a cDNA transcribed from the mRNA. In two series of experiments, one with a kappa chain probe (MOPC 41 mRNA), the other with a lambda chain probe (SAPC 178 mRNA), we analyzed a variety of myeloma DNAs and Krebs DNA. In contrast to previously reported findings (Tonegawa, S., et al. (1976) Cold Spring Harbor Symp. Quant. Biol. 41, 877), we did not observe any unique restriction map pattern in the DNA from cells which exress a given immunoglobulin gene. We also found that restriction fragments containing c region genes do not appear to transpose, while DNA sequences corresponding to other portions of the kappa and lambda mRNAs do in some cases.

Animals↗
PubMed1978

Direct demonstration of immunoglobulin kappa chain RNA in thymus T cells by in situ hybridization.

Mouse thymuses with more than 99% T cells have been reported to contain immunoglobulin kappa mRNA-like molecules (kappa RNA) in relatively large quantities. The present study was undertaken to rule out the possibility that the kappa RNA was mainly a product of a few contaminating B cells of the thymus and to determine whether all T-cell subpopulations contained kappa RNA. By in situ hybridization with DNA complementary to kappa mRNA (kappa cDNA) the following observations were made: 98.5% of thymus cell preparations hybridized with kappa cDNA; the 1.5% unlabeled cells were generally larger and paler staining than the majority of thymus cells. Only 0.015% of thymus cells were intensely labeled and appeared to be plasma cells. Also, 87% of spleen cells hybridized with kappa cDNA; most of these showed similar labeling intensity to the majority of thymus cells. The number of unlabeled cells corresponded to the percentage of hemopoietic cells and macrophages in the spleen. Spleen cells in the range of 0.37-0.85% were intensely labeled and appeared to be plasma cells. The following controls supported the conclusion that the results with thymus and spleen were due to specific hybridization: most of the kappa mRNA-deficient tissue culture cells of the plasmocytoid tumor ABPL-4 did not hybridize with kappa cDNA. The kappa mRNA-producing cells from myeloma PC 3741 hybridized in situ with kappa cDNA. Furthermore, all cells from this tumor and all spleen cells hybridized uniformly with a cDNA probe complementary to most of the total cellular poly(A)-containing RNA species of these cells. These results indicate that T cells of all types in the thymus as well as in the periphery contain substantial quantities of kappa RNA.

Animals↗
PubMed1976

Sequences related to immunoglobulin kappa chain messenger RNA in T cells.

We investigated by molecular hybridization whether T cells contain RNA sequences homologous to RNA which codes for immunoglobulin kappa-chain (k-chain). A radioactive probe of complementary DNA (cDNA) was prepared by transcription of purified k-chain mRNA from mouse myeloma MOPC-41 with reverse transcriptase (RNA-dependent-DNA nucleotidyltransferase) from avian myeloblastosis virus. The cDNA probably corresponded only to the constant region and 3'-terminus of k-chain mRNA. Kappa-chain cDNA was found to hybridize efficiently with RNA from both thymus cells and an established culture of thymoma cells. The thymus and thymoma cells contained 99.8% and 100% theta-positive cells, respectively. Quantitatively the average thymus T cell (thymus derived lymphocyte) contained about one half as much k-chain mRNA as the average spleen B cell ("bursa" dependent lymphocyte), whereas the thymoma cells contained only 1/33 as much. Control hybridizations of k-chain cDNA with myeloma and liver RNA support the conclusion that T cells in the thymus and in the thymoma cell line synthesize k-chain mRNA-like molecules. The thermal stability of hybrids of k-chain cDNA with RNA from spleen, thymus, thymoma, and another k-chain producing myeloma tumor was lower than that with MOPC-41 RNA. This finding may be due to the existence of several slightly different ck genes in the mouse as suggested by various control experiments.

B-Lymphocytes↗
PubMed1976

Analysis of immunoglobulin genes: DNA/RNA hybridization with immunoglobulin kappa-chain mRNA and isolation and translation of hybridized RNA.

Immunoglobulin kappa-chain mRNA was hybridized with DNA in order to assess the kappa-gene frequency. Kappa-mRNA was purified from membrane-bound ribosomes of mouse myeloma MOPC-41 by poly (U) chromatography and isolation of a 13S RNA by successive sucrose density gradient centrifugations. The RNA coded for kappa-chain precursor molecules in cell-free protein synthesis and essentially no other proteins. MOPC-41 kappa-mRNA hybridized with MOPC-41, MPC-11, and Krebs DNA with the same kinetics: the majority of the hybrids was formed with rare or unique DNA sequences (Cot/2 450 to 900), a small portion with highly repetitive sequences (Cot/2 5--6). The slow hybrids were well matched and the rapid hybrids were mismatched by about 4%, regardless of the DNA used. It was further investigated whether the rapid hybrids contained translatable kappa-mRNA or were due to impurities in the RNA preparations. Kappa-mRNA and globin-mRNA (as an internal standard for a unique transcript) were hybridized with DNA to Cot 20 or 48, the hybridized and unhybridized RNA were isolated by hydroxyopatite-urea chromatography and, after removal of the DNA, translated in a cell-free system. The cell-free products were analyzed by SDS-polyacrylamide gel electrophoresis and immunoprecipitation. It was found that approximately equal quantities of translatable kappa- and globin-mRNA were hybridized maximally 1.7%). The results do not support the hypothesis that kappa-mRNA is a transcript of both repetitive and unique DNA sequences.

Animals↗