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Y Lin

Publications and source records attributed to Y Lin.

At least 667 records · Page 37Linked to original sources
PubMed1987

High-level expression in Escherichia coli of a soluble and fully active recombinant interleukin-1 beta.

A complementary DNA sequence encoding monocyte interleukin-1 (IL-1), beta form/pI7, was expressed in Escherichia coli. Recombinant plasmid pDP516 was constructed by cloning and rebuilding the mature IL-1 coding sequence into an E. coli expression vector. Bacteria transformed with pDP516 constitutively produced recombinant IL-1 (r-IL-1) at 15-20% of total E. coli protein. The r-IL-1 was found to be in the soluble fraction of sonicated E. coli Bacterial r-IL-1 (DP516) has been purified to homogeneity by anion exchange and sizing column chromatography, with an apparent molecular weight of 17,500. The identity of the purified r-IL-1 was confirmed by amino acid and DNA sequencing analyses. Purified recombinant IL-1 DP516 exhibits biological activity similar to that of native monocyte IL-1 (3 approximately 4 X 10(7) units/mg). An amino-terminal deletion mutant completely abolishes the biological activity, indicating that the integrity of the IL-1 molecule might be important for its function.

Amino Acid Sequence↗
PubMed1986

Human T lymphocytes express a protein-tyrosine kinase homologous to p56LSTRA.

We have used oligonucleotide probes, based on a portion of the p60v-src autophosphorylation sequence, Glu-Asp-Asn-Glu-Tyr-Thr, to identify and characterize a cDNA from the human T-leukemia cell line, JURKAT. The JURKAT cDNA (designated ptk-JURKAT) was homologous to but distinct from the src, yes and fgr oncogenes, which encode protein-tyrosine kinases (ATP:protein phosphotransferase, EC 2.7.1.37). The ptk-JURKAT cDNA hybridized with a 2.2 kb RNA transcript from JURKAT cells and the human T-cell lymphoma line, MOLT-4, but failed to identify any transcript in two human B-cell lymphoma lines or a human erythroid-myeloid leukemia line, K562. Recently the nucleotide sequence has been established for the murine lymphocyte protein tyrosine kinase, p56LSTRA. The ptk-JURKAT cDNA appears to encode the human homolog of p56LSTRA.

Amino Acid Sequence↗
PubMed1986

The cloned cell line L10A2.J expresses natural cytotoxic activity.

The analysis of natural cytotoxicity (NC) has been hampered by the lack of cloned NC effectors. In studies reported here we show that the cloned cell line L10A2.J expresses properties similar to those of splenic NC effectors. L10A2.J cells lyse NC-sensitive targets, but do not lyse NC-resistant targets which are sensitive to lysis by natural killer (NK) or cytotoxic T lymphocytes. The mechanism by which L10A2.J cells lyse NC-sensitive targets is similar to the lytic mechanism of splenic NC effectors in that both result in the release of 51Cr from targets with a lag of 5-7 hr after effectors and targets are mixed. In addition, inhibition of protein synthesis during the in vitro assays of NC or L10A2.J lytic activity causes some NC-resistant targets to become sensitive to lysis by both NC and L10A2.J effectors. The only functional difference detected between L10A2.J and splenic NC effectors is in their recognition of targets. While L10A2.J and splenic NC effectors recognize many of the same targets (NC resistant and NC sensitive), L10A2.J, unlike splenic NC effectors, does not recognize the NK-sensitive cell line YAC-1.

Animals↗
PubMed1986

Dissociation of contact-noninhibition in vitro and tumorigenicity in vivo.

For cell lines, the correlation of the in vitro expression of contact-inhibition to the in vivo expression of the nontumorigenic phenotype, and the correlation of the expression of contact-noninhibition (i.e., focus formation) to the expression of the tumorigenic phenotype are commonly used as a means to identify, in vitro, cells which presumably have undergone malignant transformation such that, if tested, they would grow as tumors in vivo. In this report we show that while this correlation is true for contact-noninhibited transformants induced by benzo(a)pyrene (BP), a DNA mutating and demethylating agent, it is not true for contact-noninhibited transformants induced by 5-azacytidine (AZC), a DNA demethylating agent which does not have mutagenic activity. The in vitro treatment of a contact-inhibited cell line with 5-azacytidine (AZC) results in the expression of contact-noninhibited transformants, which, in vitro quantitatively and qualitatively similar to those induced by BP but unlike BP, treatment with AZC does not result in the in vivo expression of tumorigenicity.

Animals↗
PubMed1986

In vivo or in vitro selection for resistance to natural cytotoxic cell lysis selects for variants with increased tumorigenicity.

Experiments were designed to test the hypothesis that transformed cells that are NC sensitive must escape NC activity if they are to grow as tumors in normal individuals. NC-resistant variants were selected either in vivo or in vitro from NC-sensitive cell lines that grow as tumors in immunodeficient mice but not in syngeneic normal mice. The tumorigenicity of cloned NC-resistant variants was compared with the parental cell lines and to cell lines that went through the selection procedure, but after cloning remained NC sensitive. Cloned NC-resistant cell lines derived from tumors that developed in x-irradiated nude mice after the injection of an NC-sensitive cell line are tumorigenic in normal mice, whereas cloned NC-sensitive cell lines derived from the same tumors are unable to grow as tumors in normal mice. Similarly, six of seven NC-resistant cloned cell lines independently isolated after in vitro selection for NC-resistance are tumorigenic in normal mice, whereas cloned NC-sensitive cell lines isolated from the same in vitro selected populations are not tumorigenic in normal mice. Thus, either the in vivo or in vitro selection of NC-resistant cells selects for cells tumorigenic in normal mice; these findings, along with our previous observations that selection for cells tumorigenic in normal mice selects for NC resistance, provide compelling evidence that escape from NC activity is required before some transformed cells can grow as tumors in normal mice.

Animals↗
PubMed1985

In situ hybridization of putative somatostatin mRNA within hypothalamus of the rat using synthetic oligonucleotide probes.

The distribution of mRNA with high sequence homology to somatostatin mRNA within the periventricular hypothalamus of rat was assessed using in situ hybridization techniques with synthetic oligodeoxyribonucleotide probes, complementary to the 3' coding region of rat somatostatin mRNA. The probes (22- and 24-mers) were 5'-end labeled using T4 polynucleotide kinase and gamma-32P-ATP. They were used either individually or after ligation with T4 DNA ligase to form a 46-mer. Serial tissue sections (less than 10 microns) were taken from the level of the preoptic/anterior hypothalamus through the paraventricular hypothalamus. In situ hybridizations were conducted at room temperature in hybridization buffer. Neurons immunoreactive with antiserum raised against somatostatin were identified in alternate sections using standard immunocytochemical procedures. The anatomical location of the hybridization signal was determined by autoradiography. Our results show that the peri- and paraventricular hypothalamus is rich in transcripts putatively coding for somatostatin and that these transcripts are co-distributed with neurons immunoreactive with antisomatostatin immunoglobulin.

Animals↗
PubMed1985

A viral long terminal repeat in the interleukin 2 gene of a cell line that constitutively produces interleukin 2.

The gibbon leukemia cell line MLA 144 differs from every other T-lymphocyte line in that it constitutively makes interleukin 2 (IL-2) (also called T-cell growth factor) without stimulation by antigen, lectin, or tumor promoters. Previous work in which glucocorticoids were used to inhibit IL-2 production has indicated that proliferation of this cell line is dependent upon endogenously produced IL-2. We have found that the MLA 144 cell line has a copy of the gibbon leukemia virus inserted into the 3' nontranslated region of the IL-2 gene. This integration event produces a composite mRNA made up of the protein coding sequences of the IL-2 gene transcript but incorporating the viral long terminal repeat (LTR) in the 3' nontranslated region of the mRNA. This composite mRNA transcript uses the polyadenylylation signal in the viral 5' LTR and incorporates the viral transcriptional control regions. The integration event must involve only one allele of the IL-2 gene, since transcripts essentially identical to normal human IL-2 mRNA are also produced in cloned sublines of MLA 144. That the viral LTR contains a 94-base-pair repeat reminiscent of enhancer sequences in several viruses suggests that the integration of the viral LTR at the 3' end of the IL-2 gene is responsible for the constitutive production of IL-2 in the MLA 144 cell line.

Animals↗
PubMed1985

Analysis of immune surveillance of sequentially derived cell lines that differ in their tumorigenic potential.

The immune surveillance hypothesis suggests that cancer evolves as a multistage process. Further, it predicts that cells intermediate on the pathway to cancer are susceptible to host protective mechanisms, and only those variants that are able to escape the protective mechanisms are able to grow as tumors. We have isolated, as lineages, fibroblast lines that express phenotypes predicted by the surveillance hypothesis. The lineages were derived by treating nontransformed cells (N-cells) with chemical carcinogens and by isolating transformed variants in vitro. From the transformants that are tumorigenic in immune-depressed ATXFL mice but rejected by normal mice (I-cells), variants were selected in vivo that had escaped the rejection mechanism(s) and had grown as tumors in normal mice (C-cells). Thus lineages were established comprised of sequentially derived cell lines with the following phenotypes: nontransformed, transformed but susceptible to host protective mechanisms, transformed and resistant to host protective mechanisms (i.e., N----I----C). With the use of in vivo cross-protection experiments, two independently derived I-cell lines were shown to express non-cross-reactive antigens that are not expressed by the parental nontransformed N-cells (i.e., transformation-associated antigens). The transformation-associated antigens are expressed at an equivalent level on the cells that are susceptible to rejection (i.e., I-lines) and those that have escaped rejection (i.e., C-lines). In addition, although the transformation-associated antigens expressed by I-cells induce an effective immune response capable of rejecting both the I-line and C-line, the expression of these antigens on C-cells does not induce an effective immune response. The role of host defense mechanisms in the rejection of these chemically transformed I-cells and the possible mechanisms by which C-cells escape rejection are discussed.

Animals↗