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K B Marcu

Publications and source records attributed to K B Marcu.

At least 91 records · Page 5Linked to original sources
PubMed1983

c-myc Gene rearrangements involving gamma immunoglobulin heavy chain gene switch regions in murine plasmacytomas.

In murine plasmacytomas, the c-myc gene has frequently been found to undergo rearrangement by virtue of a T(12;15) chromosome translocation. The immunoglobulin heavy chain gene switch region (S alpha) constitutes the target for most of these recombinations particularly in IgA producing plasmacytomas. We sought to identify non-S alpha myc target sites in several IgG producing tumors. The c-myc target in MPC-11 (a BALB/c IgG2b producing plasmacytoma) has been cloned, localized to the Igh-C locus and identified as the gamma 2a heavy chain gene switch region (S gamma 2a). Furthermore, by Southern blot hybridization, we have determined that the S gamma 2b region is the c-myc target in two NZB IgG2b producing plasmacytomas. The potential relation between Ig class expressed and c-myc translocation target is discussed.

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PubMed1983

An African trypanosome variant surface glycoprotein gene whose expression is not activated by duplication.

A variant surface glycoprotein (VSG) of Trypanosoma brucei is encoded by a gene whose expression is not governed by duplication-transposition. There are two copies of this gene. The 5' flanking regions of the two genes are indistinguishable by restriction mapping, although each possesses approximately 5-10 Kbp of DNA which is devoid of restriction sites. All restriction enzymes tested appeared to cut genomic DNA at a uniform distance 3' of the gene. This, coupled with the observed sensitivity of both genes to BAL 31, indicates that they lie near chromosomal termini. Length variation occurs 3' of these genes in bloodstream clones and their procyclic derivatives, although the number of length variants is conserved. This suggests that length variation alone does not control VSG switching or gene expression and that constraints exist on the extent to which 3' flanking regions can vary in length.

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PubMed1983

Transcriptionally active c-myc oncogene is contained within NIARD, a DNA sequence associated with chromosome translocations in B-cell neoplasia.

NIARD (non-immunoglobulin-associated rearranging DNA) is located on mouse chromosome 15 at the break point of a commonly observed translocation event involving chromosomes 15 and 12 in murine plasmacytomas. The human cellular analogue of the v-myc oncogene of avian myelocytomatosis virus, strain MC-29, is known to reside on the distal end of human chromosome 8 and has been observed to translocate to chromosome 14 in Burkitt lymphomas. Using a cDNA clone specific for the transcript of the human c-myc gene (H c-myc), we show that the mouse c-myc (M c-myc) gene is contained within NIARD. NIARD-associated chromosome translocations occurred 1.3-2 kilobases (kb) 5' of the mouse c-myc gene where NIARD recombines with the switch region of the C(alpha) immunoglobulin gene in various murine plasmacytomas. The mouse c-myc encoding region within NIARD spanned <2.4 kb of DNA and expressed a low level of a 2.3-kb polyadenylylated RNA in BALB/c spleen. Increased (10- to 20-fold) levels of rearranged mouse c-myc transcripts (i.e., approximately 1.8-2.1 kb) were observed in plasmacytomas that have NIARD-associated chromosome translocations. Human c-myc and NIARD probes detected DNA rearrangements of human c-myc in four of seven Burkitt lymphomas. DNA sequences adjacent to the human c-myc gene recombined with the C(mu) immunoglobulin gene locus on chromosome 14 in several Burkitt lymphomas. The activation of the c-myc oncogene by chromosome translocation implicates its involvement in B-cell oncogenesis.

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PubMed1983

Hybrid gamma 2b-gamma 2a genes expressed in myeloma variants: evidence for homologous recombination.

The expressed immunoglobulin heavy chain genes of five gamma 2b-gamma 2a hybrid chain-producing variants of the mouse myeloma MPC-11 (gamma 2b, kappa) have been characterized by genomic Southern blot analysis. Results show that a hybrid gamma 2b-gamma 2a gene was formed in each variant by recombination between the expressed gamma 2b gene of MPC-11 and a gamma 2a gene. The recombination sites are within regions of marked homology between gamma 2b and gamma 2a genes: at least three and probably four variants show gamma 2b-gamma 2a recombination within the heavy chain constant region 2 (CH2) domain, while the fifth has its recombination site between the penultimate nucleotide of CH1 and the eighth nucleotide of the hinge. An unexpected finding is that the hybrid heavy chain-producing variants fall into two subgroups based on their use of different gamma 2a gene forms in hybrid gene formation. This result leads to the speculation that either a tandem gamma 2a gene duplication was present in MPC-11 prior to variant generation or mitotic recombination between chromosomes occurred in the generation of one variant subgroup. The similarity of hybrid gene formation in MPC-11 variants to that apparently responsible for concerted evolution within multigene families and hybrid protein expression in various individuals is noted, and the possible relationship between hybrid gene formation and the heavy chain class switch is discussed.

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PubMed1982

A switch region inversion contributes to the aberrant rearrangement of a mu immunoglobulin heavy chain gene in MPC-11 cells.

We describe the unique features of an aberrantly rearranged mu immunoglobulin heavy chain gene isolated from MPC-11 cells (a gamma 2b producing Balb/c plasmacytoma). A novel rearrangement has occurred 1.5 Kb 5' of the MPC-11 mu gene (denoted 18b mu) resulting in the deletion of the majority of the repetitive switch region (S mu) and 5' flanking DNA including the Joining (JH) sequences. The remainder (275 bp) of the S mu repeat has undergone a complete sequence inversion. DNA sequences 5' of the inverted S mu sequence do not resemble Variable (VH), Diversity (D), JH or their conserved flanking sequences. A DNA sequence localized 5' of the inverted S mu sequence, (p18b mu-1.4) detects a small family of homologous sequences in Balb/c DNA. The 18b mu-1.4 like sequences lack homology to S mu, exhibit flanking sequence polymorphisms in 5 out of 6 inbred mouse strains and undergo partial or complete deletion in 5 out of 10 plasmacytomas tested. Two 18b mu-1.4 homologous sequences display a higher copy number in C57Bl/6, AL/N and CAL9 mouse strains.

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PubMed1982

Nucleotide sequence and properties of the murine gamma 3 immunoglobulin heavy chain gene switch region: implications for successive C gamma gene switching.

During B lymphocyte differentiation, immunoglobulin heavy chain constant region (CH) genes undergo a unique series of DNA recombination events culminating in the CH class switch. CH switch (S) regions are located 2 kb 5' of each CH gene except delta (i.e. mu, gamma 3, gamma 1, gamma 2b, gamma 2a, epsilon and alpha). We describe the structural features of the gamma 3 switch region. Hybridization experiments show that S gamma 3 has remarkable homology to both S mu and other S gamma regions while S mu possesses limited homology to the other S gamma sequences. However, S mu possesses extensive sequence homology with S epsilon and S alpha. The nucleotide sequence of S gamma 3 reveals higher densities of S mu repetitive sequences (GAGCT and GGGGT) and another S region common sequence (YAGGTTG) than observed for S gamma 1, S gamma 2b or S gamma 2a. In addition, the conservation of S mu like repetitive sequences in S gamma regions is correlated with the 5' leads to 3' gamma gene order (i.e. S gamma 3 greater than S gamma 1 greater than S gamma 2b greater than S gamma 2a). A model is presented which suggests that the unique features of S gamma 3 may allow for successive switches from C mu to any C gamma gene.

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PubMed1982

On immunoglobulin heavy chain gene switching: two gamma 2b genes are rearranged via switch sequences in MPC-11 cells but only one is expressed.

During B lymphocytes differentiation, switches in the expression of heavy chain immunoglobulin constant region (CH) genes occur by a novel DNA recombination mechanism. We have investigated the requirements of the CH gene switch by characterizing two rearranged gamma 2b genes from a gamma 2b producing mouse myeloma (MPC-11). One of the two gamma 2b genes is present in 2-3 copies per cell (gamma 2b strong hybridizer) while the other is present in approximately 1 copy per cell (gamma 2b weak hybridizer). Genomic clones of the gamma 2b strongly hybridizing gene indicate that this is an abortive switch event between the S gamma 3 and S gamma 2b regions. However, clones of the gamma 2b weakly hybridizing gene suggest a functional rearrangement due to the presence of VH, JH and S mu sequences. The switch-recombination sites of these rearranged gamma 2b genes and those of other CH genes show a high degree of preference for the sequence AGGTTG 5' of either the S mu donor site or the appropriate CH S acceptor site. AGGTTG and its analogs are rare in the S mu region, are somewhat prevalent in s alpha and in the case of S mu are found 5' of a tandemly repeated DNA sequence (GAGCT, GGGGT) comprising most of S mu.

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PubMed1982

Non-immunoglobulin-associated DNA rearrangements in mouse plasmacytomas.

We have characterized a class of DNA rearrangements in plasmacytomas. These recombination events involve a DNA sequence whose origin is outside of the locus of the heavy chain constant region genes, CH. Therefore, we choose to refer to this sequence as non-immunoglobulin-associated rearranging DNA (NIARD). We have isolated two abortively rearranged C alpha genes, generated by NIARD events from the alpha-producing J558 myeloma. Restriction endonuclease maps of these sequences reveal two possible recombination sites in NIARD that are separated by approximately 6.5 kilobase pairs of DNA (defined as 5' and 3' sites). A NIARD rearrangement occurs in 15 out of 20 plasmacytomas tested, including gamma 3-, gamma 1-, gamma 2b-, gamma 2a-, and alpha-producers, but this event usually does not involve a CH switch (S) region. In fact, only S alpha appears to accept NIARD. However, NIARD did not undergo a rearrangement in eight IgA-producing hybridomas tested. One germ-line copy of NIARD (a 22-kilobase pair EcoRI fragment) is retained in all plasmacytomas. NIARD does not appear to possess repetitive DNA sequences homologous to S mu or S alpha. We discuss the possible role and implications of NIARD-like sequence rearrangements in allelic exclusion and chromosomal translocation events in plasmacytomas.

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PubMed1982

DNA sequence associated with chromosome translocations in mouse plasmacytomas.

A DNA sequence that generates aberrantly rearranged immunoglobulin heavy chain constant region genes in murine plasmacytomas is shown to participate in a chromosome translocation. We have previously termed this DNA sequence NIARD for non-immunoglobulin-associated rearranging DNA. NIARD rearrangements were found frequently in murine plasmacytomas but were not detected in normal lymphocytes. These rearrangements occasionally involve the switch region of the C alpha gene. In this study, DNA samples obtained from mouse-Chinese hamster somatic cell hybrid lines were digested with various restriction endonucleases and analyzed by the Southern transfer technique with a NIARD hybridization probe. These experiments show that NIARD resides on chromosome 15 in the mouse germ line. Since NIARD is found adjacent to the C alpha gene (located on chromosome 12) in some plasmacytomas, it is apparent that a translocation involving these two chromosomes has occurred. We have proposed a rcpT(12;15) model to explain our data. The implications of NIARD rearrangements for malignant transformation are discussed.

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PubMed1982

DNA rearrangements in MPC-11 immunoglobulin heavy chain class-switch variants.

Immunoglobulin heavy chain class switching has been observed in vitro. In the IgG2b-producing MPC-11 mouse myeloma cell line, IgG2a-producing cells arise at a high frequency. In some cases, switch variants producing normal-sized (Mr 55,000) gamma 2a heavy chains have arisen spontaneously from a mutagen-induced "intermediate" (ICR 9.7.1) that produces an unusually large (Mr 75,000) heavy chain. Other switch variants have been isolated directly from the parent cell line. The expressed and unexpressed gamma 2b genes of MPC-11 can be distinguished in restriction endonuclease digests of total genomic DNA so that DNA rearrangements detected in MPC-11 variants can be directly associated with one or the other of these two genes. We describe here DNA rearrangements occurring on the expressed heavy chain chromosome of several MPC-11 gamma 2a switch variants and on the expressed chromosome of the ICR 9.7.1 intermediate. Our data indicate that all of these variants express the parental heavy chain variable region (VH) gene, supporting previous protein studies. We provide mapping data for the expressed gene of both ICR 9.7.1 and one of the IgG2a-producing variant cell lines (ICR 9.9.2.1) derived from it and discuss the advantages of an in vitro switching system for examining the dynamics of the immunoglobulin heavy chain class switch.

Animals↗
PubMed1982

Rearrangements and deletions of immunoglobulin heavy chain genes in the double-producing B cell lymphoma I.29.

The B cell lymphoma I.29 consists of a mixture of cells expressing membrane-bound immunoglobulin M (IgM) (lambda) and IgA (lambda) of identical idiotypes. Whereas most of the cells express either IgM or IgA alone, 1 to 5% of the cells in this tumor express IgM and IgA simultaneously within the cytoplasm and on the cell membrane (R. Sitia et al., J. Immunol. 127:1388-1394, 1981; R. Sitia, unpublished data). When IgM+ cells are purified from the lymphoma and passaged in mice or cultured, a portion of the cells convert to IgA+. These properties suggest that some cells of the I.29 lymphoma may undergo immunoglobulin heavy chain switching, although it is also possible that the mixed population was derived by a prior switching event in a clone of cells. We performed Southern blotting experiments on genomic DNAs isolated from populations of I.29 cells containing variable proportions of IgM+ and IgA+ cells and on a number of cell lines derived from the lymphoma. The results were consistent with the deletion model for heavy chain switching, as the IgM+ cells contained rearranged mu genes and alpha genes in the germ line configuration on both the expressed and nonexpressed heavy chain chromosomes, whereas the IgA+ cells had deleted both mu genes and contained one rearranged and one germ line alpha gene. In addition, segments of DNA located within the intervening sequence 5' to the mu gene, near the site of switch recombination, were deleted from both the expressed and the nonexpressed chromosomes. Although mu genes were deleted from both chromosomes in the IgA+ cells, the sites of DNA recombination differed on the two chromosomes. On the expressed chromosome, Smu sequences were recombined with S alpha sequences, whereas on the nonexpressed chromosome, Smu sequences were recombined with S gamma 3 sequences.

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PubMed1981

Expression of an antigen receptor on T cells does not require recombination at the immunoglobulin JH-C mu locus.

Considerable evidence has accumulated suggesting that the antigen receptor(s) on T cells is coded for by genes for the variable (V) region of the immunoglobulin heavy (H) chains. In B cells, a complete gene for the immunoglobulin VH region is formed by somatic recombination of VH and joining region heavy chain (JH) gene segments [through an intermediate diversity(D) region gene segment]. In an attempt to determine whether a complete immunoglobulin VH region is expressed on T cells that bear an antigen receptor, we analyzed the restriction map of the JH-C mu locus in genomic DNA from two cloned murine cytotoxic T-lymphocyte (CTL) lines specific for the x-ray-induced leukemia RL male 1. We found no rearrangement of the JH C mu locus in the CTL lines, indicating that the T-cell antigen receptor(s) in these CTLs is not coded for by a complete immunoglobulin VH gene formed by joining of VH, (DH), and JH genes. In addition, we determined that C mu genes on both chromosomes were present and that there was no rearrangement of the C alpha, C kappa, or lambda chain genes in these CTL cells.

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PubMed1980

Mouse rDNA nontranscribed spacer sequences are found flanking immunoglobulin CH genes and elsewhere throughout the genome.

When a cloned 6 kb Eco RI-Sal I fragement of mouse ribosomal gene nontranscribed spacer DNA (rDNA NTS) was used to screen a BALB/c mouse gene library, 25% of the recombinant phage hybridized with it. In situ hybridization experiments and characterization of 12 clones selected using this probe supported the idea that sequences homologous to this rDNA NTS region are scattered throughout the genome. Subsequently, sequences homologous to mouse rDNA NTS were found flanking mouse mu, alpha and gamma 2b immunoglobulin CH genes. One region was localized 3' to the mu coding sequence, an area which has been identified as an intervening sequence between the secreted C mu heavy chain terminus and the C terminal portion of the membrane-bound C mu heavy chain.

Animals↗
PubMed1980

5' flanking region of immunoglobulin heavy chain constant region genes displays length heterogeneity in germlines of inbred mouse strains.

Genomic Southern blotting analysis reveals that a 5' flanking DNA sequence located 1.5-2.0 kb upstream from the C mu and C alpha genes undergoes extensive length variation in the germlines of inbred and wild mice. In addition, genomic clones of the BALB/c C mu gene undergo deletion events during their propagation in Charon 4A when maintained in RecA+ bacterial strains. These deletion events occur between the JH cluster and the C mu gene and approximately 2.0 kb 5' of the C alpha gene, and may encompass several kb of DNA. Deletion events are capable of yielding a group of C mu clones which differ in size by units of 100-200 bp. The site of length variation in the mouse germline corresponds to the location of these cloning-derived deletion events, suggesting that both phenomena are reflections of intrinsic genetic properties of these Ig gene 5' flanking sequences.

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