Identification of a transcriptionally compromised allele of c-MYC in a North American family.
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Alleles↗
Biomedical subjects
D Siwarski
Publications and source records attributed to D Siwarski.
Double light chain producing lymphocytes: an enigma of allelic exclusion.
The infrequent double light chain producing lymphocyte (DLCPL) is discussed in the context of allelic exclusion. Principally allelic selection rather than allelic exclusion would suggest a role for the DLCPL in the normal B cell population rather than as an aberrance of B cell malignancy. Found primarily in the periphery, it is uncertain at what stage of B cell ontogeny the DLCPL might reside. Nevertheless, through the possible presentation of two functional surface receptors, the DLCPL could be capable of recognizing both self and nonself epitopes.
Alleles↗
Generation of monospecific peptide antibodies to the DNA binding domain of p53.
The DNA binding domain (DBD) is the most mutated region of p53 in tumors and has proven to be relatively resistant to the generation of specific antibodies. Template assembled synthetic peptide (TASP) synthesis of a peptide derived from the DBD creates a highly immunogenic molecule without the need for large carriers such as keyhole limpet hemocyanin (KLH). In addition, a rapid means of generating monoclonal antibodies can be achieved through immunization in conjunction with ABL/MYC retrovirus injection into recipient mice. In this paper, we demonstrate that an antibody generated by this means, KH2, reacts specifically with the DBD of p53. To date, this is the first example of a peptide immunogen used successfully in ABL/MYC monoclonal antibody production. KH2 is also the first example of a monospecific antibody that directly binds to and, by definition, assumes the conformation of the DNA binding region of p53.
Amino Acid Sequence↗
Restricted immunoglobulin variable region (Ig V) gene expression accompanies secondary rearrangements of light chain Ig V genes in mouse plasmacytomas.
The many binding studies of monoclonal immunoglobulin (Ig) produced by plasmacytomas have found no universally common binding properties, but instead, groups of plasmacytomas with specific antigen-binding activities to haptens such as phosphorylcholine, dextrans, fructofuranans, or dinitrophenyl. Subsequently, it was found that plasmacytomas with similar binding chain specificities not only expressed the same idiotype, but rearranged the same light (V(L)) and heavy (V(H)) variable region genes to express a characteristic monoclonal antibody. In this study, we have examined by enzyme-linked immunosorbent assay five antibodies secreted by silicone-induced mouse plasmacytomas using a broader panel of antigens including actin, myosin, tubulin, single-stranded DNA, and double-stranded DNA. We have determined the Ig heavy and light chain V gene usage in these same plasmacytomas at the DNA and RNA level. Our studies reveal: (a) antibodies secreted by plasmacytomas bind to different antigens in a manner similar to that observed for natural autoantibodies; (b) the expressed Ig heavy genes are restricted in V gene usage to the V(H)-J558 family; and (c) secondary rearrangements occur at the light chain level with at least three plasmacytomas expressing both kappa and lambda light chain genes. These results suggest that plasmacytomas use a restricted population of B cells that may still be undergoing rearrangement, thereby bypassing the allelic exclusion normally associated with expression of antibody genes.
Amino Acid Sequence↗
cDNA isolation, expression, and chromosomal localization of the mouse pcph proto-oncogene.
We report here the isolation and characterization of a cDNA from mouse thymus encoding the murine homolog of the protein product of the Syrian hamster Pcph proto-oncogene. The single open reading frame identified in the cDNA sequence encoded a protein predicted to have 428 amino acids, which shared 93.7% amino acid identity with the Syrian hamster Pcph within the first 412 residues but had a shorter, highly dissimilar C-terminus. Northern and western analyses revealed that Pcph mRNA and protein were widely distributed in mouse embryo and adult tissues, with the highest expression in adults detected in kidney and liver. The mouse Pcph proto-oncogene was mapped by linkage analysis to within 3.3+/-2.3 cM of Pkch-rs1 on chromosome 12. These data should prove valuable in designing studies to define the cellular function of the Pcph proto-oncogene.
Amino Acid Sequence↗
Encyclopedia of the mouse genome VII. Mouse chromosome 15.
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Animals↗
Structure and expression of the c-Myc/Pvt 1 megagene locus.
A chromosomal translocation (Tx) that interrupts the transcription of either c-Myc or Pvt 1 is the principal lesion in many B cell malignancies including Burkitt's Lymphoma (BL), AIDs-NHL, mouse plasmacytoma (Pct) and possibly multiple myeloma (MM). There is a restriction associated with this Tx such that only the immunoglobulin (Ig) heavy chain gene is found juxtaposed to c-Myc and only the Ig light chain gene is found juxtaposed to Pvt 1. Over the past several years, our laboratory has been instrumental in the elucidation of the structure of the mouse Pvt 1 locus as a means of understanding the relationship between these two divergent Txs which, nevertheless, produce indistinguishable disease phenotypes. In the mouse, we have identified a uniform Pvt1/Ig Ck fusion product which is consistently found in all tumors harboring Pvt 1 associated Txs. We have recently constructed transgenic mice harboring a translocated Pvt 1/Ck segment in order to determine whether 1). these mice produce the Pvt 1/Ck fusion product 2). these mice are immunocompromised and 3). these mice develop tumors of a B cell origin.
Amino Acid Sequence↗
Genomic instability in MycER-activated Rat1A-MycER cells.
The deregulated expression of c-Myc protein is associated with the non-random locus-specific amplification of the dihydrofolate reductase (DHFR) gene. This study was performed to determine whether additional chromosomal aberrations occur when c-Myc protein levels are up-regulated for prolonged periods. To this end, we have used Rat1A-MycER cells, which allow the experimental regulation of Myc protein levels. We examined the genomic stability of Rat1A-MycER cells cultivated in either the absence or the presence of estrogen, which reportedly activates the chimeric MycER protein in these cells. Following prolonged periods of MycER activation, Rat1A-Mycer cells exhibited irreversible chromosomal aberrations. The aberrations included numerical changes, chromosome breakage, the formation of circular chromosomal structures, chromosome fusions, and extrachromosomal elements.
Animals↗
Molecular cloning, chromosomal mapping, and expression of the mouse p107 gene.
Progression through the G1 phase of the cell cycle is regulated, in part, by the pRB-family proteins, pRB and p107. The basis for this regulation is due to a network of interactions between the pRB-family proteins, pRB, p107, and p130; the E2F-family of transcription factors; and cyclins D, E, and A. One of the pRB-family proteins, p107, has also been found to bind to the transactivation domain of the c-Myc proto-oncogene. This region in c-Myc is frequently mutated in tumors such as Burkitt's lymphoma, HIV-associated lymphoma, and multiple myeloma. The binding of p107 and regulation of c-Myc may conceivably be disrupted not only by mutations in c-Myc, but possibly by mutations in p107. In order to determine if mutations in p107 are indeed present in mouse B-cell tumors which exhibit a lower frequency of c-Myc mutation, we have cloned the mouse p107 cDNA and compared this sequence with its human counterpart. We find that the extreme N-terminal and C-terminal regions are the most conserved between human and mouse p107 sequences. Chromosomal positioning of the locus for p107 (designated Rbl1) as well as E2f1 to the distal end of mouse Chromosome (Chr) 2 also suggests a close but unlinked genetic relationship between these cell cycle regulatory transcription factors.
Animals↗
Encyclopedia of the mouse genome V. Mouse chromosome 15.
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Animals↗
Chromosomal localization of the gastric and brain receptors for cholecystokinin (CCKAR and CCKBR) in human and mouse.
Receptors for cholcystokinin (CCK) can be pharmacologically classified into at least two distinct subtypes, CCKAR and CCKBR. In an effort to determine whether the CCKA and CCKB receptors may be associated with certain CNS or gastrointestinal diseases, we have localized and compared the human and mouse chromosomal loci encoded by the CCKAR and CCKBR genes. The gene encoding the CCKA receptor maps to a syntenic region of human chromosome 4 and mouse chromosome 5. The CCKB receptor gene, on the other hand, resides on a syntenic region of human chromosome 11 and distal mouse chromosome 7. Localization of the CCK receptors with two dopamine receptors, DRD5 (4p15.1-p15.3) and DRD4 (11p15), provides the interesting possibility of coinvolvement in neuropsychiatric or CNS illnesses.
Animals↗
A murine antibody to Shigella dysenteriae type 1 employs V-genes that contain a rearranged codon for the lambda light chain.
The cDNA coding for a hybridoma anti Shigella dysenteriae type 1 antibody (3707 E9) has been cloned, and sequenced. Binding patterns with fragments of the bacterial polysaccharide antigen had already been studied in detail. The VH sequence utilizes the VH441 gene, first identified amongst beta-(1,6)galactan-binding antibodies, while the VL is closely related to the V lambda 1 gene. We found that the VL3707 E9 gene employed a VL-J combinatorial joining leading to a rare Trp-->Leu substitution at position L96.
Amino Acid Sequence↗
Amplified extrachromosomal elements containing c-Myc and Pvt 1 in a mouse plasmacytoma.
After adaptation of a mouse plasma cell tumor, MOPC265, to culture, we have found several unique chromosomal alterations in addition to the T(12;15) translocation and trisomy 11 frequently observed in plasmacytomas. Among these alterations is a specific coamplification of the c-Myc and Pvt 1 gene loci from mouse chromosome 15. Further analysis by fluorescence in situ hybridization demonstrates that the amplicons of c-Myc and Pvt 1 exist as extrachromosomal elements as well as within intact chromosomes. Most importantly, the presence of both Pvt 1 and c-Myc in these extrachromosomal elements indicates ongoing coselection for these loci in the propagation of MOPC265.
Animals↗
Chimeric transcripts with an open reading frame are generated as a result of translocation to the Pvt-1 region in mouse B-cell tumors.
Some mouse plasmacytomas exhibit a t(6;15) chromosomal translocation in which the breakpoint resides within the Pvt-1 locus located 260 kilobases (kb) downstream of c-myc on mouse chromosome 15. In this report, we show that the Pvt-1 locus does not exhibit allelic exclusion in that Pvt-1 transcripts continue to be expressed from the non-translocated allele in t(6;15) plasmacytomas. From the translocated allele, we find chimeric transcripts containing a short 57-bp segment of Pvt-1 (termed Pvt-1a) spliced directly to the immunoglobulin constant region sequence (Ig-Ck). These short transcripts have replaced a Jk segment with a trytophan residue via RNA splicing and contain a continuous open reading frame (ORF) from Pvt-1a through Ck. Since this Pvt-1a/Ck transcript is found in all 3 t(6;15) plasmacytomas examined, regardless of the location of the chromosomal breakpoint, we suggest that the Pvt-1a/Ck chimera may have a functional role in the development of mouse plasmacytomas.
Amino Acid Sequence↗
Assignment of the protein kinase C delta polypeptide gene (PRKCD) to human chromosome 3 and mouse chromosome 14.
The protein kinase C (pkc) enzymes are a family of serine-threonine protein kinases, each encoded by a distinct and separate gene. The chromosomal locations of human PRKCA, PRKCB, and PRKCG have previously been established. We now report that PRKCD, a novel member of the pkc gene family, maps to human chromosome 3. The chromosomal location of Pkcd has also been determined in the mouse by analysis of recombination frequency in an interspecific panel of backcross mice. We find that the locus encoding pkcd resides proximal to nucleoside phosphorylase (Np-2) and Tcra on mouse chromosome 14 in a region syntenic with human 3p.
Animals↗
Molecular cloning, sequencing, chromosomal localization and expression of mouse p21 (Waf1).
The recent discovery that expression of Waf1 (p21), an inhibitor of cyclin-dependent kinases, is induced by the tumor suppressor p53 provides an important linkage between growth suppression and the cell cycle. We report here the cloning and sequencing of a mouse p21 cDNA that contains the entire coding region. Hybridization of the mouse p21 probe in Southern blot analyses confirms that p21 is a single-copy gene and that the corresponding locus, Waf1, lies proximal to H-2 on mouse chromosome 17. In northern analyses, the expression of p21 is found in most normal mouse tissues, but a surprising lack of correlation is found between mRNA levels of p21 and p53. In order to determine which regions of p21 are most evolutionarily conserved, we have compared the cDNA sequences for the entire p21 coding region in 13 different mouse strains or species and the human p21 sequence. We conclude that two regions (corresponding to human codons 21-60 and 130-164) are strongly conserved in p21 and that these regions may represent domains that are especially critical to a functional p21 protein.
Amino Acid Sequence↗