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D Germain

Publications and source records attributed to D Germain.

At least 19 recordsLinked to original sources
PubMed1992

The pro-region of the Kex2 endoprotease of Saccharomyces cerevisiae is removed by self-processing.

We have produced in the baculovirus/insect cells expression system a soluble secreted form of the Saccharomyces cerevisiae Kex2 endoprotease. This secreted enzyme was purified and its NH2-terminal sequence determined. The NH2-terminal sequence started at residue Leu109 of the sequence deduced from the KEX2 gene nucleotide sequence, showing that the Kex2 enzyme is produced as a proenzyme. Residue Leu109 is preceded by a pair of basic amino acid residues (Lys107-Arg108) which is a potential processing site for the Kex2 endopeptidase. Furthermore, expression of an inactive form of this truncated enzyme resulted in the production of a protein with a higher molecular weight. These observations suggest that the pro-region of Kex2 endoprotease is removed by a self-processing event.

Amino Acid Sequence↗
PubMed1992

Expression of the Saccharomyces cerevisiae Kex2p endoprotease in inset cells. Evidence for a carboxy-terminal autoprocessing event.

The pheromone-processing Kex2p endoprotease of Saccharomyces cerevisiae has been difficult to characterize due to its low level of expression in yeast cells. To overcome this problem, we have overexpressed Kex2p using the baculovirus/insect cell expression system. Spodoptera frugiperda Sf9 insect cells infected with a recombinant baculovirus, containing the complete KEX2 gene which encodes the Kex2p protease (814 amino acids), accumulate an 120-kDa functional form of the enzyme. The inhibition profile of the insect-cell-derived endoprotease is similar to that of the yeast enzyme. The recombinant infected insect cells also secrete into the medium about half of the total Kex2p activity produced. Deleting the carboxyl-terminal tail and the transmembrane domain of Kex2p (Kex2 delta p, 666 amino acids) does not measurably interfere with the enzyme characteristics and results in the secretion of up to 90% of the total enzyme activity. The truncated form, Kex2 delta p, of the endoprotease accumulates in the cell supernatant to 6.7 x 10(5) U/l. The molecular mass of the secreted forms for both the wild-type Kex2p and Kex2 delta p is the same (70 kDa) and is 50-kDa lower than the intracellular form. This result implicates a processing event which gives rise to shorter extracellular forms of both the wild-type Kex2p and Kex2 delta p and which trims their carboxy termini upsteam of amino acid 666. This processing event requires the integrity of the Ser385 of the Kex2p active site.

Animals↗
PubMed1992

BTG1, a member of a new family of antiproliferative genes.

The BTG1 gene locus has been shown to be involved in a t(8;12)(q24;q22) chromosomal translocation in a case of B-cell chronic lymphocytic leukemia. We report here the cloning and sequencing of the human BTG1 cDNA and establish the genomic organization of this gene. The full-length cDNA isolated from a lymphoblastoid cell line contains an open reading frame of 171 amino acids. BTG1 expression is maximal in the G0/G1 phases of the cell cycle and is down-regulated when cells progress throughout G1. Furthermore, transfection experiments of NIH3T3 cells indicate that BTG1 negatively regulates cell proliferation. The BTG1 open reading frame is 60% homologous to PC3, an immediate early gene induced by nerve growth factor in rat PC12 cells. Sequence and Northern blot analyses indicate that BTG1 and PC3 are not cognate genes. We then postulate that these two genes are the first members of a new family of antiproliferative genes.

3T3 Cells↗
PubMed1992

Association of t(15;17) and t(8;21) in the initial phase of an acute promyelocytic leukemia.

Two clones were observed at the initial phase of an acute myelogenous leukemia (AML): 46,XX,t(15;17) and 46,XX,t(8;21),t(15;17). Clinical, immunologic, and morphologic findings were in favor of expression of both chromosomal anomalies. Relapse occurred after 12 months of complete remission with typical acute promyelocytic leukemia (APL) syndrome when t(15;17) alone was then most predominant.

Antigens, CD↗
PubMed1991

A chromosome 12 coding region is juxtaposed to the MYC protooncogene locus in a t(8;12)(q24;q22) translocation in a case of B-cell chronic lymphocytic leukemia.

We performed molecular cloning and sequencing of the breakpoints of a new chromosomal translocation involving the MYC protooncogene locus. This secondary t(8;12)(q24;q22) was associated with a primary t(11;14)(q13;q32) translocation in a case of B-cell chronic lymphocytic leukemia (CLL) in blastic transformation. In this leukemia, Northern blot and nuclease analyses SI showed that MYC was strongly expressed with initiation of the transcription at both the 5' and 3' promoters as observed in Burkitt's lymphomas; no coding change was observed in MYC putative regulatory sequences. The breakpoint on chromosome 8 mapped to the 3' end of the MYC locus, in a region containing a potential Z-DNA tract, and where we identified two DNase 1 hypersensitive sites. A rearranged MYC gene fragment was cloned and shown to contain chromosome 12 information by Southern blot analysis and by in situ hybridization. A genomic probe subcloned from the isolated region of the chromosome 12 recognized a 1.8 kb transcript in virtually all the tissues tested but a preferential expression of this new gene, which we termed BTG1 (for B-cell translocation gene 1) was observed in the CLL cells and in tissues of lymphoid origin. This chromosome 12 coding sequence is conserved in evolution and a transcript of similar size is present in murine tissues.

Animals↗
PubMed1991

Expression in yeast of a cDNA copy of the K2 killer toxin gene.

A cDNA copy of the M2 dsRNA encoding the K2 killer toxin of Saccharomyces cerevisiae was expressed in yeast using the yeast ADH1 promoter. This construct produced K2-specific killing and immunity functions. Efficient K2-specific killing was dependent on the action of the KEX2 endopeptidase and the KEX1 carboxypeptidase, while K2-specific immunity was independent of these proteases. Comparison of the K2 toxin sequence with that of the K1 toxin sequence shows that although they share a common processing pathway and are both encoded by cytoplasmic dsRNAs of similar basic structure, the two toxins are very different at the primary sequence level. Site-specific mutagenesis of the cDNA gene establishes that one of the two potential KEX2 cleavage sites is critical for toxin action but not for immunity. Immunity was reduced by an insertion of two amino acids in the hydrophobic amino-terminal region which left toxin activity intact, indicating an independence of toxin action and immunity.

Amino Acid Sequence↗
PubMed1991

Prohormone processing by yeast proteases.

Investigations of the precursors of alpha-pheromone and killer toxin in the yeast Saccharomyces cerevisiae have defined the genes coding (KEX1 and KEX2) for the proteases which are responsible for their processing. In addition to processing at pairs of basic residues it is evident that yeast can also process at monobasic sites. We present data on the Kex1p and Kex2p enzymes, their cellular localization, and their post-translational modification. In addition initial characterisation of the monobasic specific protease and the isolation of mutants defective in this activity are presented. The use of the yeast system as a model for the processing of mammalian prohormones is discussed.

Amino Acid Sequence↗
PubMed1990

Break in the BCL1 locus is closely associated with intermediate lymphocytic lymphoma subtype.

The t(11;14)(q13;q32) is a recurring translocation associated with some chronic B-cell lymphocytic malignancies; the putative protooncogene BCL1, located at the chromosome band 11q13, can be involved during the translocation process. In order to determine if BCL1 rearrangement is associated with a particular subtype of lymphoma, we analysed 131 B-cell non-Hodgkin's lymphoma samples by Southern blot analysis, using a BCL1 probe. The BCL1 locus was rearranged in 9 out of 25 (36%) cases of intermediate lymphocytic cell lymphomas (ILL), in 1 out of 8 cases of diffuse small cleaved cell lymphoma, in 1 out of 12 cases of diffuse mixed cell lymphoma, and in 1 out of 21 cases of diffuse large cell lymphoma. In contrast, BCL1 was never found rearranged in any of the 46 follicular lymphomas analysed. The BCL2 gene was in germ-line configuration in all ILL. Sequential hybridization of Southern blots with JH, C mu, and BCLI probes identified comigrating fragments in only one case of ILL, which suggests that, in all the other cases, either the rearrangement of BCL1 did not result from a t(11;14) translocation or the break on chromosome 14 occurred outside the JH or C mu regions. These results indicate that rearrangement of the BCL1 locus may be closely associated with ILL and could be considered as a genotypic marker of this lymphoma subtype.

Blotting, Southern↗
PubMed1990

Correlations between cytogenetics and morphology in myelodysplastic syndromes.

In order to detect possible relationships between cytogenetic abnormalities and morphologic features in myelodysplastic syndromes (MDS), 48 patients with MDS were investigated. Clonal cytogenetic abnormalities were present in bone marrow cells from 27 patients (56%). The most frequent single anomaly was del (5 q) (10 cases), followed by monosomy 7 (3 cases), trisomy 8 (3 cases) and del (20 q) (2 cases). Complex anomalies were present in 6 patients. Morphologically, according to the French-American-British (FAB) classification: 17 cases were considered as refractory anemia (RA), 17 as RA with excess of blasts (RAEB), 2 as RAEB in transformation, 2 as acquired idiopathic sideroblastic anemia and 10 as chronic myelomonocytic leukemia. With regard to the FAB classification, del (5 q) was often associated with RA and complex cytogenetic anomalies with RAEB. When myelodysplasia was studied in individual myeloid lineages, del (5 q) was associated with hypolobulated megakaryocytes, monosomy 7 with micromegakaryocytes and complex chromosomal anomalies with the association of two or more features of dysmegakaryocytopoiesis. Del (11 q) was associated with increased iron storage and del (20 q) with marked dyserythropoiesis. No correlation was observed between cytogenetic anomalies and features of dysgranulocytopoiesis.

Adult↗
PubMed1990

Intracellular proteolytic processing of proopiomelanocortin in heterologous COS-1 cells by the yeast KEX2 endoprotease.

We have transiently expressed the yeast KEX2 gene together with the proopiomelanocortin (POMC) cDNA in COS-1 cells. Characterization of the POMC-related immunoreactive peptides by gel permeation and reversed-phase high pressure liquid chromatography showed that the KEX2 enzyme was active and capable of carrying out cleavage of POMC to release the authentic maturation product beta-endorphin(1-31). Peptides resembling beta-lipotropin, the amino terminal glycopeptide, and ACTH(1-39) were also detected as major products in the cell extracts. Our results indicate that the KEX2 enzyme can proteolytically release from POMC a set of peptides similar to that normally found in interior pituitary.

Adrenocorticotropic Hormone↗
PubMed1990

The yeast KEX-2-processing endoprotease is active in the Golgi apparatus of transfected NIH 3T3 fibroblasts.

Proteolytic processing of polyprotein precursors at pairs of basic amino acids is a prerequisite for the generation of bioactive peptide hormones. While the mammalian endoproteases responsible for these cleavages are yet to be identified, this function has been unequivocally assigned in yeast to the product of the KEX-2 gene. To study the molecular mechanisms involved in polyprotein processing, we have transfected the yeast KEX-2 gene into mouse NIH 3T3 fibroblasts and established a new cell line (called 2N-DK) where the KEX-2 endoprotease is permanently expressed. Immunofluorescence studies show that the KEX-2 enzyme is retained within the Golgi of the 2N-DK cells. The evidence for this cellular location is supported by measurement of intracellular and extracellular KEX-2 enzyme activity. In this permanently transfected cell line, KEX-2 activity is exclusively intracellular, in contrast to the situation previously described in transiently infected cell lines, where extracellular KEX-2 activity was detected. Furthermore, infection of 2N-DK cells with a recombinant retrovirus expressing a cDNA coding for porcine proopiomelanocortin (POMC) resulted in the synthesis of POMC and its efficient processing into beta-lipotropin and beta-endorphin, two of its physiologically authentic maturation products. These results suggest that in the fibroblast cell line 2N-DK, proteolytic processing of POMC by KEX-2 endoprotease occurs in the Golgi apparatus.

Amino Acid Sequence↗
PubMed1989

A translocation involving a specific breakpoint (q35) on chromosome 5 is characteristic of anaplastic large cell lymphoma ('Ki-1 lymphoma').

Two cases of non-Hodgkin's lymphoma are reported in which a chromosomal translocation was observed involving the same site (q35) on the long arm of chromosome 5. The other breakpoint involved in the translocation was chromosome 2 (p23) in one case and chromosome 3 (q12) in the other. Both cases were large cell lymphomas expressing CD30 antigen ('Ki-1 lymphoma'). One was clearly of T lymphoid origin, the other probably B cell derived. One other case of a Ki-1 lymphoma with 2;5 translocation (involving the same breakpoint on chromosome 5) has been reported previously, and it is suggested that this cytogenetic abnormality may be specifically associated with Ki-1 lymphoma. The literature contains a further eight cases of lymphoid neoplasms with a translocation involving a breakpoint at q35 on chromosome 5. They have all been described as cases of 'malignant histiocytosis', but the present findings make it likely that these cases were in reality also examples of Ki-1 lymphoma. The breakpoint at the q35 region on chromosome 5 is close to the position of the fms proto-oncogene, suggesting that an abnormality affecting this gene might possibly play a causal role in 'Ki-1 lymphoma'. However, DNA restriction fragment analysis of the present cases showed no evidence that the breakpoint on chromosome 5 involves the fms gene or its immediate vicinity.

Adolescent↗
PubMed1988

Initial clonal acute lymphoblastic transformation of chronic lymphocytic leukemia with (11;14) and (8;12) chromosome translocations and acquired homozygosity.

A 69-year-old woman presented with chronic lymphocytic leukemia (CLL) diagnosed after bone marrow recovery following intensive chemotherapy for acute lymphoblastic leukemia. The retrospective diagnosis of initial blastic transformation of CLL was made. The patient eventually died, 5 months after initial blastic phase, from a blastic relapse of her CLL. Immunologic and karyotypic studies of the lymphoid cells at different times during the evolution of the disease provided evidence that both the small lymphocytes and the large blastic cells originated from the same clone since they carried the same surface markers and the same (11;14) (q13;q32) translocation. A subpopulation of cells carried in addition a t(8;12) (q24;q22) together with the loss of the normal chromosome 8 and homozygosity for the abnormal der(8). The possibility that this second population might correspond to the blast cells and that the occurrence of the t(8;12) with homozygosity might be linked to blastic transformation of the CLL is discussed.

Aged↗