Cloning of breakpoints in and downstream the IGF2 gene that are associated with overexpression of IGF2 transcripts in colorectal tumours

The human IGF2 gene belongs to a group of imprinted genes clustered on the short arm of chromosome 11, band p15.5. It contains 9 exons and spans over 30 kb. IGF2 mRNA overexpression has been reported in human tumours and in some inherited growth disorders. It was recently demonstrated that IGF2 mRNA overexpression contributes to tumour progression and that loss of parental imprinting as well as altered transcription factors are contributing to this overexpression. We have reported structural alterations in the 3' region of the IGF2 gene in two colorectal tumours that overexpressed the IGF2 transcript by 200- and 800-fold. We cloned by the vectorette-PCR strategy, genomic DNA fragments containing the breakpoints from these tumours. The sequencing of these fragments positioned the breakpoint 2 kb downstream the IGF2 gene in one tumour, and in exon 9 in the second. Both breakpoints occurred in regions containing repetitive elements: a TGGA repeat we have identified downstream the gene, and the (CA)n repetition in exon 9. We hypothesize that a negative regulatory element, located downstream the IGF2 gene, has been deleted following these structural alterations and leads to IGF2 gene overexpression.

Molecular characterization of a novel subtilisin inhibitor protein produced by Streptomyces venezuelae CBS762.70

We report here on the isolation and identification of a gene coding for a novel subtilisin inhibitor (VSI) isolated from Streptomyces venezuelae CBS762.70. The vsi gene was isolated on a 5-kb chromosomal PvuII fragment as identified by DNA sequencing and inhibitor activity testing of the gene product. Primer extension studies revealed that the mRNA transcriptional start point was situated at -37 and -36 relatively to the ATG start codon assuming the presence of solely one promoter. Vsi promoter strength was about double of those of ermE-P1a and aph-P1, as tested with the mRNA production of the aphII gene preceded by the respective promoters. Translation of the vsi coding sequence revealed a 28 amino acids long signal peptide. The mature VSI protein consists of 118 amino acids of which 87% was verified by N-terminal amino acid sequence analysis. Compared with the already known Streptomyces proteinase inhibitors, VSI shows a relatively high amino acid identity in the conserved domains. Nevertheless, only a maximum amino acid identity of 56.1% was noticed and some highly conserved residues were substituted in VSI. As a consequence, VSI could be classified within a separate group of Streptomyces subtilisin inhibitors.

Line probe assay for rapid detection of drug-selected mutations in the human immunodeficiency virus type 1 reverse transcriptase gene

Upon prolonged treatment with various antiretroviral nucleoside analogs such as 3'-azido-3'-deoxythymidine, 2',3'-dideoxyinosine, 2',3'-dideoxycytidine, (-)- beta-L-2', 3'dideoxy-3'thiacytidine and 2',3'-didehydro-3'-deoxythymidine, selection of human immunodeficiency virus type 1 (HIV-1) strains with mutations in the reverse transcriptase (RT) gene has been reported. We designed a reverse hybridization line probe assay (LiPA) for the rapid and simultaneous characterization of the following variations in the RT gene: M41 or L41; T69, N69, A69, or D69; K70 or R70; L74 or V74; V75 or T75; M184, I184, or V184; T215, Y215, or F215; and K219, Q219, or E219. Nucleotide polymorphisms for codon L41 (TTG or CTG), T69 (ACT or ACA), V75 (GTA or GTG), T215 (ACC or ACT), and Y215 (TAC or TAT) could be detected. In addition to the codons mentioned above, several third-letter polymorphisms in the direct vicinity of the target codons (E40, E42, K43, K73, D76, Q182, Y183, D185, G213, F214, and L214) were found, and specific probes were selected. In total, 48 probes were designed and applied to the LiPA test strips and optimized with a well-characterized and representative reference panel. Plasma samples from 358 HIV-infected patients were analyzed with all 48 probes. The amino acid profiles could be deduced by LiPA hybridization in an average of 92.7% of the samples for each individual codon. When combined with changes in viral load and CD4+ T-cell count, this LiPA approach proved to be useful in studying genetic resistance in follow-up samples from antiretroviral agent-treated HIV-1-infected individuals.

Cloning and sequence analysis of a newly identified Brucella abortus gene and serological evaluation of the 17-kilodalton antigen that it encodes

A thus far unknown gene encoding a Brucella abortus protein has been isolated from a lambda gt11 expression library probed with sera from Brucella-infected sheep. Sequence analysis of the cloned gene revealed the presence of an open reading frame of 158 amino acids encoding a protein of 17.3 kDa (calculated molecular mass). The recombinant B. abortus protein, expressed in Escherichia coli, and the corresponding Brucella melitensis protein migrated at the same apparent molecular masses as shown by Western blotting (immunoblotting). Among a series of serum samples from B. melitensis- or B. abortus-infected sheep and cows, 51 and 39%, respectively, showed a signal at 17 kDa on Western blot analysis of total protein extract from Brucella bacteria. These figures amount to 70 and 61% for sheep and cattle, respectively, in a competitive enzyme-linked immunosorbent assay with a specific monoclonal antibody. These data indicate that the 17-kDa antigen may be useful for serological diagnosis of Brucella infection.

Purification and sequence of rat extracellular superoxide dismutase B secreted by C6 glioma

An enzyme which converts radical oxygen, produced by phorbol 12-myristate 13-acetate activated neutrophils, into nonluminescent products is secreted by rat C6 glioma. The enzyme was purified from chemically defined conditioned media and identified as an extracellular superoxide dismutase (EC-SOD). The purified enzyme is distinct from human EC-SOD C (Hjalmarsson, K., Marklund, S. L., Engström, A., and Edlund, T. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 6340-6344) by its elution from heparin-Sepharose at 300-400 mM NaCl, its pI of 6.1-7.2, and its native M(r) of 85,000 +/- 20,000. The rat EC-SOD is a dimer with a subunit M(r) of 34,000-36,000 and is extensively modified by post-translational processing. Although rat EC-SOD has a high sequence homology with the catalytic center and the polybasic heparin-binding site near the COOH terminus of human EC-SOD C, its NH2-terminal sequence and the sequences flanking the heparin-binding site differ substantially. The sequence of the isolated rat EC-SOD cDNA fully confirms the data obtained from amino acid sequence analysis. The amino acid sequence of the enzyme and its biochemical properties support its identification as the rat EC-SOD B.

Cloning and characterization of the 5'-flanking region of the mouse tartrate-resistant acid phosphatase gene

Little information is available on the molecular mechanisms controlling osteoclastic bone resorption. We used tartrate-resistant acid phosphatase (TRAP) to begin to investigate the regulation of bone resorption at the molecular level. TRAP is expressed at high levels in osteoclasts and may play an important role in the bone resorptive process. Therefore, we isolated the murine TRAP gene from a mouse spleen genomic library and characterized its promoter. A restriction map was generated for the 17 kb TRAP insert. A 2 kb SmaI fragment, containing the 5'-flanking region, was subcloned and the nucleotide sequence determined. Sequence analysis of the SmaI fragment revealed the presence of numerous candidate transcription factor binding sequences, including those for AP1 and H-APF-1. The H-APF-1 site matches the consensus sequence for the IL-6-regulated transcription factor. An intron was identified at -1 to -393 bp relative to the ATG. The presence of an intron was confirmed by PCR analysis of RNA isolated from murine osteoclasts. Primer extension analysis indicated the presence of a transcription initiation site at -552 bp from the ATG. The region from -1846 to 2bp relative to the ATG initiation codon drove the transient expression of a luciferase reporter gene when transfected into HRE H9 rabbit endometrial cells. PMA treatment of HRE H9 cells enhanced luciferase transcription approximately threefold. These data suggest that the TRAP promoter is complex and contains multiple regulatory elements. The availability of the TRAP promoter may also permit production of transgenic mice, which can be used to develop previously unavailable osteoclast cell lines.

Assignment of the mouse tartrate-resistant acid phosphatase gene (Acp5) to chromosome 9

Tartrate-resistant acid phosphatase is a marker enzyme for osteoclasts, the multinucleated cell responsible for bone resorption. Interspecific somatic whole cell hybrids and karyotypically simple microcell hybrids were used to map the gene encoding tartrate-resistant acid phosphatase (Acp5) to mouse Chromosome 9. Acp5 is therefore a member of a syntenic family of genes that map to human chromosome 19p13.1-p13.3 and mouse Chromosome 9.

Evidence for an autocrine/paracrine role for interleukin-6 in bone resorption by giant cells from giant cell tumors of bone

Interleukin-6 (IL-6) is a multifunctional cytokine whose role in osteoclastic bone resorption has not been clearly defined. Therefore, we have used giant cells, which express many features of osteoclasts, from giant cell tumors of bone as a model to examine the role that IL-6 may play in human osteoclastic bone resorption. We found that conditioned medium from 24-h cultures of highly purified giant cells (10(6)/ml) contained large amounts of IL-6 (37.9 +/- 8.8 ng/ml), similar to the amount of IL-6 produced by tumor stromal cells (29.8 +/- 11.5 ng/ml). Giant cells and stromal cells from giant cell tumors expressed IL-6 mRNA, as indicated by polymerase chain reaction analysis and in situ hybridization studies, and immunohistochemical techniques demonstrated that the giant cells expressed IL-6 receptors. The addition of a neutralizing antibody to IL-6 significantly decreased the area of dentine resorbed by purified giant cells in a dose-dependent manner, and the addition of IL-6 to cultures of purified giant cells pretreated with anti-IL-6 restored the resorbing capacity of the giant cells. These data suggest that IL-6 may act as both an autocrine and a paracrine factor for human osteoclasts and play an important role in the bone-resorbing capacity of these cells.

Effects of stem cell factor on osteoclast-like cell formation in long-term human marrow cultures

Stem cell factor (SCF) is a newly described hematopoietic growth factor that stimulates the growth of primitive hematopoietic progenitors and mast cells. Since the osteoclast precursor is hematopoietic in origin, we tested SCF for its capacity to stimulate the formation of osteoclast-like multinucleated cells (MNC) in long-term human marrow cultures. These MNC express an osteoclast phenotype and form resorption lacunae on calcified matrices. Addition of SCF alone (0.1 pg/ml to 100 ng/ml) to long-term marrow cultures did not increase MNC formation. However, treatment of these cultures sequentially with SCF for 1 week followed by 1,25-(OH)2D3 for the second and third weeks of culture significantly enhanced MNC formation. [3H]Thymidine incorporation studies showed that SCF increased the proliferation of MNC precursors. These data suggested that SCF was acting on early MNC precursors. We then tested the capacity of SCF to stimulate the formation of colonies of committed precursors for osteoclast-like MNC. SCF (20 pg/ml to 20 ng/ml) enhanced osteoclast precursor formation in unfractionated bone marrow mononuclear cells but was unable to increase osteoclast precursor formation when a highly purified population of hematopoietic precursors was used as the target cells for SCF. These data suggest that SCF works in concert with other factors produced by nonhematopoietic marrow cells to increase the precursor pool for osteoclasts and that other factors, such as 1,25-(OH)2D3, complete the differentiation process to the mature osteoclast.

Cloning of DNA sequences encoding foreign peptides and their expression in the K88 pili

A genetic system that allows the cloning of a peptide-coding sequence in the Escherichia coli K88ac and K88ad pilin genes and their expression as recombinant pili has been constructed. Two insertion vectors were created by subcloning the pilin genes in a pBR322 plasmid and replacing the coding sequence of two nonconserved clusters by a linker. The K88ac helper genes were subcloned in the compatible pACYC184 plasmid, and expression of pili by bacteria carrying both plasmids occurred by complementation. Two peptide-coding sequences of the influenza hemagglutinin were cloned in both insertion vectors, and recombinant pilins were shown to be assembled in pili. One recombinant pilus was shown to elicit antibodies against the synthetic peptide in immunized rats. The somatostatin-coding sequence was cloned in both vectors and led in one case to detectable pilus production. The fused somatostatin was shown to be recognized by specific monoclonal and polyclonal antibodies.