Showing papers by "Carlo M. Croce published in 1986"

Analysis of the structure, transcripts, and protein products of bcl-2, the gene involved in human follicular lymphoma.

Abstract: We have determined that the bcl-2 (B-cell leukemia/lymphoma 2) gene is transcribed into three overlapping mRNAs, and we have cloned bcl-2 cDNA sequences. Sequence analysis of the bcl-2 cDNA clones and comparison of their sequences to their genomic counterparts indicate that the bcl-2 gene contains at least two exons. The three bcl-2 transcripts, which are 8.5, 5.5, and 3.5 kilobases (kb) long, overlap within the first exon, but only the 8.5-kb and 5.5-kb transcripts contain sequences of the second exon. The 8.5-kb and 5.5-kb transcripts seem to use different polyadenylylation sites. Sequence analysis of the cDNA clones corresponding to the 5.5-kb and 3.5-kb mRNAs indicates that the two bcl-2 transcripts carry two overlapping open reading frames, one of which is 717 nucleotides long and codes for a protein (bcl-2 alpha) of 239 amino acids and a molecular mass of 26 kDa, while the other codes for a protein of 205 amino acids (bcl-2 beta, molecular mass 22 kDa) that is identical to bcl-2 alpha except at the carboxyl terminus. The bcl-2 protein products in follicular lymphomas with or without bcl-2 rearrangements are identical to the normal bcl-2 products.

Molecular cloning and nucleotide sequence of a full-length cDNA for human alpha enolase.

Abstract: We previously purified a 48-kDa protein (p48) that specifically reacts with an antiserum directed against the 12 carboxyl-terminal amino acids of the c-myc gene product. Using an antiserum directed against the purified p48, we have cloned a cDNA from a human expression library. This cDNA hybrid-selects an mRNA that translates to a 48-kDa protein that specifically reacts with anti-p48 serum. We have isolated a full-length cDNA that encodes p48 and spans 1755 bases. The coding region is 1299 bases long; 94 bases are 5' noncoding and 359 bases are 3' noncoding. The cDNA encodes a 433 amino acid protein that is 67% homologous to yeast enolase and 94% homologous to the rat non-neuronal enolase. The purified protein has been shown to have enolase activity and has been identified to be of the alpha type by isoenzyme analysis. The transcriptional regulation of enolase expression in response to mitogenic stimulation of peripheral blood lymphocytes and in response to heat shock is also discussed.

Localization of the human pim oncogene (PIM) to a region of chromosome 6 involved in translocations in acute leukemias

Abstract: The human homolog, hpim, of the murine pim-1 gene, which is activated in murine T-cell lymphomas by insertion of retrovirus proviral genomes in the pim-1 region, has been molecularly cloned; the cloned probe has been used to map the hpim locus to human chromosome region 6p21 by somatic cell hybrid analysis and chromosomal in situ hybridization. The hpim gene is expressed as a 3.2-kilobase mRNA in various human cell lines of hematopoietic lineage, most dramatically in the K562 erythroleukemia cell line, which contains a cytogenetically demonstrable rearrangement in the 6p21 region. A characteristic chromosome anomaly, a reciprocal translocation t(6;9)(p21;q33), has been described in myeloid leukemias and could involve the hpim gene.

Human histone genes map to multiple chromosomes

Abstract: Histone genes were mapped to at least three human chromosomes by Southern blot analysis of DNAs from a series of mouse-human somatic cell hybrids (using 32P-labeled cloned human histone DNA as probes). Chromosome assignment was confirmed by in situ hybridization of radiolabeled histone gene probes (3H-labeled) to metaphase chromosomes. One human histone gene cluster (lambda HHG41) containing an H3 and H4 gene resides only on chromosome 1, whereas other clusters containing core (H3, H4, H2A, and H2B) alone (lambda HHG17) or core together with H1 histone genes (lambda HHG415) have been assigned to chromosomes 1, 6, and 12. These results suggest that the multigene family of histone coding sequences that reside in a series of clusters may be derived from a single cluster containing one each of the genes for the five principal classes of histone proteins. During the course of evolution, a set of events, probably involving reduplication, sequence modification, and recombination, resulted in the present pattern of human histone gene distribution among several chromosomes.

The human c-ros gene (ROS) is located at chromosome region 6q16----6q22.

Abstract: The human homolog, c-ros, of the transforming gene, v-ros, of the avian sarcoma virus, UR2, has been isolated from a human genomic library A single-copy fragment from the human c-ros genomic clone has been used to map the human c-ros homolog (ROS) to human chromosome region 6q16----6q22 by somatic cell hybrid analysis and chromosomal in situ hybridization Thus, the c-ros gene joins the c-myb oncogene, which is distal to the c-ros gene on the long arm of human chromosome 6, as a candidate for involvement in chromosome 6q deletions and rearrangements seen in various malignancies

The gene encoding the T-cell surface protein T4 is located on human chromosome 12.

Abstract: The surface glycoproteins T4 and T8 define functionally distinct populations of T lymphocytes. We have obtained cDNA and genomic clones encoding the T4 molecule and used these as probes to determine the chromosomal location of this gene. Genomic blotting experiments, along with in situ hybridization analyses, indicate that the T4 gene resides on the short arm of human chromosome 12, at region p12-pter. Thus, the T4 gene is not linked to any known member of the immunoglobulin gene family, including its counterpart gene, T8, which resides on human chromosome 2 immediately distal to the immunoglobulin kappa locus.

Chromosomes, genes, and cancer.

Abstract: THE "MODERN" ERA of tumor cytogenetics began in the 1950s and accelerated rapidly with the development of so-called banding techniques in the 1970s. During this period, chromosome studies of neoplasms added significantly to our understanding of various aspects of tumor biology. The recognition that most neoplasms have visible cytogenetic alterations contributed to general acceptance of the view that somatic genetic changes are important in tumorigenesis. In addition, the demonstration that in a given tumor all the neoplastic cells often have the same karyotypic change, or related changes, helped to indicate the derivation of most tumors from a single altered cell. Presumably, the specific somatic genetic change, often recognizable at the chromosome level, confers on the progenitor cell a selective growth advantage, allowing its progeny to expand as a neoplastic "clone" of unicellular origin. The further demonstration that, in general, karyotypic abnormalities are more extensive in advanced tumors has also added importantly to our understanding of the phenomenon of tumor progression. It led to the hypothesis that neoplasms become more aggressive with time because of the sequential appearance in the neoplastic clone of subpopulations of cells with additional alterations in genetic makeup. Neoplastic cells show increased genetic instability and are thus more likely than normal cells to generate such genetic variants. In this concept of "clonal evolution," most of these genetic variants that arise in a tumor cell population do not survive, but those few mutants that have an additional selective growth advantage expand to become predominant subpopulations within the neoplasm, and demonstrate the characteristics of more aggressive growth and increased "malignancy" that we recognize as tumor progression. The continued presence of multiple subpopulations in the neoplasm provides the basis for the heterogeneity that is also typically observed in malignant tumors. Cytogenetic data contributing to these evolving concepts have been incorporated into several recent reviews of the mechanisms of tumor progression.1I2 Most current developments in tumor cytogenetics, however, have related to another aspect that has been increasingly recognized as techniques have improved: specific alterations in particular chromosomes are associated, with different degrees of consistency, with specific types of tumors, or with neoplasia in general.3'4 It has been suggested that these nonrandom karyotypic changes might indicate sites in the genome where particular genes important in carcinogenesis are located, and provide clues as to how the function of such "oncogenes" might be significantly altered. Much of the initial support for this hypothesis has come from the study of specific reciprocal chromosome translocations in various hematopoietic tumors such as Burkitt's lymphoma and chronic myelogenous leukemia (CML), in which alteration in structure and/or function of proto-oncogenes, the human homolog of retroviral oncogenes, has been demonstrated. At the same time, chromosomal changes in other tumors, reflecting gain or loss of genetic material, have suggested a critical role for oncogene dosage in some instances of carcinogenesis. This brief review of recent findings will focus on this aspect of the cytogenetics and related molecular genetics of neoplasia, with emphasis primarily on our own recent studies in leukemia and lymphoma.

Regulation of translocated c-myc genes transfected into plasmacytoma cells.

Abstract: We have transfected two translocated c-myc oncogene clones, derived from two human lymphomas carrying the t(8;14) chromosome translocation, into mouse plasmacytoma cells to study the regulation of their expression. In one case, the transfected clone contained the two coding exons of the c-myc oncogene translocated to an immunoglobulin heavy-chain switch region; in the other case, the two coding exons were translocated 5' of the enhancer element located between the heavy-chain joining region (JH) and the switch region S mu. Nuclease S1 protection experiments indicate that only the c-myc translocated 5' of the enhancer element is transcribed in the plasmacytoma cells. Thus, 5'-truncation of the c-myc gene per se does not lead to c-myc deregulation. Further, since the level of c-myc transcripts in the parental human lymphoma cells was 3- to 4-fold higher than in the transfectants, it seems likely that additional elements within the heavy-chain locus may play a role in the enhancement of c-myc gene transcription in lymphoma cells.