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Biomedical subjects

C J Larsen

Publications and source records attributed to C J Larsen.

At least 91 records · Page 5Linked to original sources
PubMed1990

t(2;18) and t(18;22) variant chromosomal translocations and bcl-2 gene rearrangements in human malignant lymphomas.

Most human follicular lymphomas bear the specific t(14;18) translocation that juxtaposes the 3' region of bcl-2 to the IgH gene on chromosome 14q+. In some rare cases, t(2;18) and t(18;22) translocations have been observed that involve bcl-2 and either Ig kappa or lambda genes. Strikingly, in these cases all the breakpoints on chromosome 18 are located in the 5' end the bcl-2 gene. These rearrangements are very similar to those recently found in a significant proportion of CLL. Thus, bcl-2 rearrangements in malignant lymphomas cluster in at least three regions: the so-called major breakpoint region (mbr) and minor cluster region (mcr) in more than 85% of t(14;18) translocation, and the newly characterized region 5' of the gene. We propose to call this new cluster region vcr (for variant cluster region).

Chromosomes, Human, Pair 14↗
PubMed1989

Structural alterations of the BCR and ABL genes in Ph1 positive acute leukemias with rearrangements in the BCR gene first intron: further evidence implicating Alu sequences in the chromosome translocation.

In the Philadelphia positive bcr negative acute leukemias (Ph1+bcr- AL), the chromosomal breakpoints on chromosome 22 have been shown clustered within 10.8kb (bcr2) and 5kb (bcr3) fragments of the first intron of the BCR gene. We previously reported that the breakpoints were localized in Alu repeats on chromosomes 9 and 22 in a Ph1+bcr- acute lymphoblastic leukemia with a rearrangement involving bcr2. Molecular data of two other Ph1 translocations, one a Ph1+bcr- acute myeloblastic leukemia in the bcr2 region, and the other an acute lymphoblastic leukemia in the bcr3 region are presented. In the former, the breakpoints on chromosomes 9 and 22 are localized in Alu repeats, in regions with two inverted Alu sequences, as in our previously reported case. In the second leukemia, the breakpoints are not located in Alu sequences, but such repeats are found in their vicinity. The implications of these findings are discussed.

Base Sequence↗
PubMed1989

Nucleolar proteins identified in human cells as antigens by sera from dogs with autoimmune disorders.

In the course of a systematic screening of sera from dogs suffering from autoimmune disorders, three sera were shown by indirect immunofluorescence to characteristically label the nucleoli and nucleoplasm of human cell lines (Hep-2 and HeLa). This pattern of staining persisted throughout the cell cycle, except for mitosis when the fluorescence was localized in extrachromosomal areas. By immunoblotting nuclear and subnuclear fractions, three polypeptides of 110,000, 95,000, and 45,000 Da apparent molecular weight were identified, which reacted with all three sera. By means of affinity purification, it was shown that an antibody specific for any one of the three proteins also reacts with the two others. This antigenic cross-reactivity suggested regions of structural homology shared by the three proteins. Indeed, treatment of nucleoli with high concentrations of DNase I containing residual proteolytic activity resulted in the disappearance of the 110- and 95-kDa proteins and the concomitant appearance of a doublet of 45-kDa proteins. Subnuclear localization studies indicated that all three polypeptides were located in both nucleoli and nucleoplasm. Significantly, the 110-kDa protein differs from the major nucleolar protein, nucleolin, by its electrophoretic mobility in two-dimensional gels, its location in nucleoli and in nucleoplasm, its absence in nucleolar organizer regions of chromosomes, and its differential solubility of DNase I. Therefore, the three antigenically related species reported in this study constitute a new class of nucleolar proteins.

Animals↗
PubMed1988

Characterization by human antibodies of two HeLa cell proteins which are related to Xenopus laevis transcription factor TFIIIA.

The sera of two patients with autoimmune disorders recognize in HeLa cell extracts two proteins with apparent molecular masses of 37,000 (p37) daltons and 32,000 daltons (p32). These proteins are non covalently associated with 5S RNA and sediment as 7-10 S particles in sucrose density gradients. Both proteins are antigenetically related to TFIIIA, a previously described protein of Xenopus laevis, which is known as a 5S RNA transcription factor and occurs in oocytes as a noncovalent complex with 5S RNA. Like TFIIIA, HeLa cell proteins p37 binds in vitro to 5S RNA and to cloned 5S RNA genes. These results suggest that protein p37 fulfils in HeLa cells a function similar to that of TFIIIA in amphibian oocytes, ie control of 5S RNA transcription.

Animals↗
PubMed1988

[Genetic polymorphism and susceptibility to cancer].

Proto-oncogenes, which have been widely implicated in the pathogenesis of malignant human tumors, frequently demonstrate restriction fragment length polymorphism (RFLP). Population studies of such restriction alleles is of potential interest for genetic analysis of cancer susceptibility. Some of the initial date of Krontiris et al (1985) showing a significant increase of rare c-ha-ras-l alleles in individuals with tumors, have been confirmed in certain types of cancer (breast cancer, lung adenocarcinoma), whereas others have been refuted (myelodysplasia, melanoma, colon adenocarcinoma). Other significant associations have been found between other proto-oncogene RLFPs and tumors (c-mos and breast cancer, c-raf and non Hodgkins lymphoma, L-myc and lung carcinoma metastasis). Although they are controversial, these studies should be extended, in order to determine whether the presence of certain alleles is a contributing factor in the development of certain tumors.

Disease Susceptibility↗
PubMed1988

Molecular mechanisms of a t(8;14)(q24;q11) translocation juxtaposing c-myc and TcR-alpha genes in a T-cell leukaemia: involvement of a V alpha internal heptamer.

We have recently described a t(8;14)(q24;q11) translocation which appeared secondarily in a non-established acute T-cell leukaemia and involved the 3' region of c-myc proto-oncogene and the alpha chain of the T-cell receptor gene (TcR-alpha). In order to elucidate the mechanism of the translocation, we have isolated breakpoint regions from normal and recombinant chromosomes. Our results show that the translocation occurred at the 3' end of a V alpha segment in the proximity of recombination signal sequences (5'-heptamer-23bp spacer-nonamer-3'). Interestingly, an inverted heptamer internal to the V alpha segment was found at two nucleotides 5' of the break. Nucleotide sequence analysis also revealed the presence of homologous signal sequences on chromosome 8, suggesting that the recombination enzymatic system played an important role in the generation of the translocation. This hypothesis is supported by the addition of N nucleotides and the loss of only three nucleotides during the rejoining process. These data established the involvement of a V alpha segment and its recombination signals in the mechanisms of t(8;14) translocations in T-cell leukaemias.

Amino Acid Sequence↗
PubMed1988

[Lack of expression of the protein p53 gene in a human T-cell leukemia line].

Expression of the gene encoding the nuclear phosphoprotein p53 (a proto-oncogene classified in the same functional family as c-myc and E1a adenovirus gene) was examined in a human T-cell leukemia (KE-37R cell line). No p53 (or a modified product) could be detected by immunoprecipitation with monoclonal antibodies P Ab 421 and P Ab 122 in KE-37R cell extracts, and no p53-specific RNA was characterized by Northern blot analysis. Southern blot using a murine p53 cDNA clone as a probe, did not reveal any gross rearrangement in the structure of the gene. However, this molecular probe was not suited for investigating the 5' end of the gene which contains the promoter and the non coding exon 1. It is interesting to notice that in KE-37R cells, c-myc has been activated by a t(8; 14) (q24; q11) translocation, suggesting that the c-myc product might substitute to some functions normally requiring p53.

Cell Line↗
PubMed1988

Molecular cloning of a 5' segment of the genomic phl gene defines a new breakpoint cluster region (bcr2) in Philadelphia-positive acute leukemias.

Molecular rearrangements of Ph1 chromosome, the hallmark of CML, are clustered in a 5.8-kb DNA segment, the so-called breakpoint cluster region (bcr) of the phl gene that is localized to chromosome 22q11. In Ph1-positive (Ph1+) ALLs, the rearrangements have been shown to involve either the 5.8-kb bcr (called bcr+) or a region upstream of bcr in the 5' end of the phl gene (bcr-). To gain insight into the rearrangements occurring in Ph1+ acute leukemias, a 64-kb DNA fragment from the 5' end of phl was analyzed in order to generate molecular probes covering 40 kb of the phl gene first intron. A panel of seven cases of bcr-Ph1+ acute leukemia (three nonlymphocytic and four lymphocytic) was investigated with these intron 1-derived probes. Strikingly, in six of the seven leukemias, the breakpoints were located in a 10.8-kb DNA segment, defining a new bcr which appears to be specific for Ph1+ acute leukemias. By analogy with the CML bcr region located in the 3' part of the phl gene, we propose to designate this 10.8-kb fragment bcr2.

Chromosome Mapping↗
PubMed1987

PSL, a nuclear cell-cycle associated antigen is increased during retinoic acid-induced differentiation of HL-60 cells.

PSL(p55) is a nuclear 55kD antigen present in various mammalian cell systems, which has been first identified by use of human autoimmune antibodies (Barque et al. 1983, EMBO J. 2, 743). It has been shown to be associated with interphase chromatine and to be synthesized in during the S phase of the cell cycle. In this work, we have analysed the status of PSL in promyelocytic HL-60 human cells in exponential or stationary growth, or undergoing granulocytic differentiation in presence of Retinoic acid. By use of 2-dimensional electrophoresis, PSL was found to be composed of two acidic proteins designated p55A and p55B. Unexpectedly, estimated 10-20 fold higher amounts of each species were found in cells treated for 5 days with 10(-6)M Retinoic acid, than in asynchronously growing cells or resting cells. Moreover, the p55A protein was phosphorylated during the process. On the basis of these results, PSL appears to be involved in some steps of the granulocytic differentiation process.

Cell Cycle↗
PubMed1987

In vivo and in vitro stimulation by antitumor drugs of the topoisomerase II-induced cleavage sites in c-myc proto-oncogene.

Stimulation of topoisomerase II cleavage activity by antitumor drugs with or without DNA intercalative ability has been tested in vivo on the c-myc proto-oncogene. Two human tumor cell lines (N417 and HL60 cells) were treated with mAMSA, OH-9-ellipticine, VM26, and BD-40 (an aza-ellipticine analog), and DNA breaks were mapped in the gene locus by Southern blot hybridization with c-myc probes. Most of the major cleavage sites induced in vivo by drugs in the 5' end of c-myc were also observed in vitro using purified topoisomerase II and a c-myc gene DNA insert. Moreover, they closely mapped to some DNAse I hypersensitive sites, the presence of which reflects gene activity. DNA from drug treated cells probed with a human beta 1 globin pseudogene, and the c-mos proto-oncogene did not reveal topoisomerase II cleavage bands, suggesting that topoisomerase II-mediated drug activity may correlate with gene activity.

Amsacrine↗
PubMed1987

[Study, at the gene level, of the activation of topoisomerase II by antitumor agents].

Most experimental data clearly suggest that antitumor agents including DNA intercalative molecules (acridine derivatives, ellipticine and derivatives), or non intercalative ones (epipodophyllotoxines), exert their cytotoxic activity by stabilizing DNA-Topoisomerase II complexes. This phenomenon can be revealed by the presence of DNA breaks upon protein denaturing treatment. In this work, BD-40, an ellipticine analog has been shown to interact in vivo with Topoisomerase II. Moreover, cleavage sites generated by the drug treatment in human proto-oncogene c-myc appear to be mostly localized in the 5' end of the gene locus, which contains regulatory elements. Some of these sites are in a striking correspondence with DNAse I hypersensitive sites, which reportedly reflect the state of activity of genes.

Alkaloids↗