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Biomedical subjects

J C Lang

Publications and source records attributed to J C Lang.

48 records · Page 3Linked to original sources
PubMed1984

Transcriptional regulation of a herpes simplex virus immediate early gene is mediated through an enhancer-type sequence.

An enhancer-type sequence has been identified in the promoter region for the herpes simplex virus type 1 (HSV-1) immediate early (IE) mRNA 3. The enhancer-type activity is host cell dependent, being greater in human cells and Syrian hamster cells (the usual host cell for in vitro propagation of HSV) than in Chinese hamster or mouse cells. Enhancer activity is stimulated up to 10-fold after superinfection by tsK, a temperature-sensitive mutant of HSV-1. The induction of enhancer activity is independent of de novo protein synthesis, showing that trans-activation is effected by a component of the virion. We propose that trans-regulation of IE mRNA 3 is mediated through an enhancer-type sequence, and that this provides one explanation for previously described regulation of HSV IE mRNAs by virion components.

Animals↗
PubMed1983

Characterization of eukaryotic transcriptional control signals by assay of herpes simplex virus type 1 thymidine kinase.

We describe the characteristics of a general assay for eukaryote transcription-control sequences using the herpes simplex virus (HSV) thymidine kinase (tk) gene. After transfection of cultured cells with tk-containing recombinant plasmids, two assays were used to measure gene expression: short term or transient levels of tk mRNA and TK enzyme activity, and the rate of biochemical transformation from a TK- to a TK+ phenotype in selective growth medium (HAT). Deletion of the endogenous tk promoter results in 500-fold inactivation of gene expression. Replacement with exogenous transcription-control sequences from the human epsilon globin, mouse beta major globin, simian virus 40 and Moloney murine sarcoma virus (MoMuSV) genomes results in reactivation of gene expression. The presence of enhancers or activators of gene expression can also be conveniently measured. The transient expression assay ranged over two orders of magnitude while the transformation assay was almost two orders of magnitude more sensitive using the same recombinants. Analysis of the transcription-control domains in the MoMuSV LTR sequences shows the presence of both an enhancer and a promoter whose activity equalled that of the tk endogenous promoter. Insertion of the LTR promoter between the LTR enhancer and the tk promoter had little effect on modulating gene expression, suggesting no absolute preference for proximal promoters by this element. The different levels of gene expression obtained appears to be mediated by transcriptional control of full-length tk mRNA. There was an apparent correlation between the results obtained with the transient expression and transformation assays. However, cultured transformed cells all contained roughly the same levels of tk DNA, tk mRNA and tk enzyme activity. We propose that initial expression levels have a major effect in determining the transformation efficiency but that additional genetic controls are superimposed in cells grown in selective HAT medium.

Animals↗
PubMed1980

Comparison of antithyroid drug metabolism in the rat and guinea pig.

The thyroid accumulation, metabolism and urine excretion of (35S) propylthiouracil was compared in the guinea pig and the rat. Per gram thyroid tissue, the guinea pig thyroid took up much less drug than the rat, metabolised it faster and had a shorter t 1/2 for total 35S and free (35S) propylthiouracil. Liver metabolism, clearance of the drug from the serum and excretion in the urine were also considerably faster in the guinea pig. It is likely that a much larger dose of propylthiouracil would need to be administered to induce goitre in the guinea pig than is necessary in the rat.

Animals↗
PubMedDate not supplied

Cis-platin responsive sequences in the human c-myc promoter.

We have transfected recombinant plasmids carrying 5' c-myc sequences linked to the reporter gene chloramphenicol acetyl-transferase (cat) and to the selectable marker aminoglycoside phosphotransferase (aph) into rat fibroblasts and obtained stable transfectants. The response to cis-platin of these cell lines was studied. At 5 X 10(-5) M concentration cis-platin stimulates cat gene expression 9 and 11 fold respectively in cell lines containing constructs with c-myc promoter sequences truncated at -2319 and -350 relative to c-myc RNA start site P1. A third cell line expressing a myc/cat recombinant truncated at -290 shows no response to cis-platin, thus defining a cis-platin responsive element between coordinates -290 and -350 on the myc promoter region.

Base Sequence↗
PubMedDate not supplied

Oncogene transfection of mink lung cells: effect on growth characteristics in vitro and in vivo.

Three sublines have been derived from the parental line Mv1Lu by transfection with normal and mutated Ha-ras, and myc oncogenes, and subsequent cloning. All the oncogenes have increased the growth rate of the cell in vitro, increased their plating efficiency in monolayer and suspension, and reduced their serum dependence. Growth in vivo as xenografts in nude mice has also been increased. Very few tumours were generated from the parental line and those that did form did so after a prolonged lag period, while the transfected lines produced tumours with 100% efficiency, and a short lag period. In general the effects of ras transfection were more extreme, with the highest growth rates and plating efficiencies in vitro and the shortest lag period and doubling times in vivo. There was no increase in plasminogen activator activity as a result of transfection, and the invasive behaviour of the lines in organotypic culture was broadly similar.

Animals↗
PubMedDate not supplied

Immortalization by truncated myc or ras genes and synergism between myc and ras genes in cell transformation.

Human c-myc and normal or mutant T24 H-ras1 genes either linked to the regulatory sequences of the human metallothionein IIa gene or unlinked have been employed individually or in combination to transfect early passage Chinese hamster lung cells. Since the c-myc and H-ras1 genes are present in recombinant plasmids carrying the aminoglycoside phosphotransferase (aph), gene transfectants were selected in the presence of geneticin. A synergistic effect has been observed between myc and H-ras1 genes in measurement of both the number of geneticin resistant colonies obtained and the parameters of morphological transformation and anchorage independence. Out study also demonstrates the ability of truncated myc and ras genes to induce immortalization of hamster cells.

Animals↗
PubMedDate not supplied

The structure and function of eukaryotic enhancer elements and their role in oncogenesis.

Transcriptional enhancers have now been identified near or within a large number of viral and cellular genes. They are cis-acting regulatory sequences generally capable of elevating transcription from a linked gene in a distance and orientation independent manner. More recent evidence suggests that this activity may be modulated in a host-cell-specific manner. Enhancer function in some cases at least appears to be controlled by the operation of trans-acting factors within the host cell. Occasionally enhancers may also be responsible for repression of gene transcription. It has now become clear that the development of some cancers may be linked with the activity of enhancer sequences. It is likely that this process involves subversion of the normal regulatory mechanisms which control expression of proto-oncogenes through the interposition of exogenous, cis-acting enhancer sequences. The evidence comes from two sources, firstly a strong association between the action of enhancer sequences and some forms of naturally occurring cancers, and secondly, the induction of neoplastic transformation in susceptible cells by genetically manipulated oncogenes under the transcriptional control of enhancer elements.

Animals↗
PubMedDate not supplied

The expression of C-myb in human metastatic melanoma cell lines and specimens.

The rapidly increasing incidence of malignant melanoma and lack of effective systemic therapy for advanced disease has given rise to the need for new approaches. The suggestion that c-myb may be an important gene in the control of melanoma proliferation prompted the exploration of its expression in several metastatic melanoma cell lines and specimens. Initial Northem hybridization showed undetectable expression of c-myb in the cell lines, although it was very strongly expressed in the K-562 cell line. Therefore, c-myb expression was examined utilizing primers and RT-PCR on the five melanoma cell lines and thirty-two metastatic melanoma specimens. There was very low expression in the two cell lines (UISO Mel-1 and 3) that were nontumorigenic, whereas there was a 10 fold increase in expression in the tumorigenic cell lines. In the metastatic specimens the expression varied by over 100 fold between the lowest and highest specimens. The expression of c-myb in tumor specimens was in general greater than matched normal specimens, save for skin which had moderate expression. In general, there did not appear to be any correlation between the clinical characteristics of the various specimens and the amount of c-myb expression. However, females with lymph node metastases had somewhat lower expression than males. The fact that significant melanoma specimens have altered expression of c-myb, coupled with the previous inhibition of melanoma growth by antisense c-myb, suggests that there may be a potential role for c-myb antisense therapy in the treatment of this tumor.

Female↗