Characterization of clones of HIV-1 infected HuT 78 cells defective in gag gene processing and of SIV clones producing large amounts of envelope glycoprotein.

Single-cell clones of HIV-1 (FRE-3) or SIV/Mne infected HuT 78 cells were obtained by plating dilutions of virally infected HuT 78 cells on a monolayer of sheep choroid plexus cells in 96-well microtiter plates. Several of these clones produce HIV-1 virus mutants that accumulate the gag precursor polyprotein and lack a functional protease. These protease-deficient viruses are non-infectious and consist of aberrant "immature" virus particles as determined by electron microscopy. Several SIV mutants are also described that produce large amounts of either the envelope glycoprotein gp120 or the nucleic acid binding gag protein. These mutants are useful for the purification of these retroviral proteins, in developing assays of protease inhibitors, and in preparing SIV envelope protein vaccines.

Inhibition of tumor cell proliferation by a novel growth regulator from placenta: modulation of membrane phosphorylation and oncogene expression.

The tumor specific inhibition of thymidine uptake by a negative growth regulator isolated from the maternal part of the bovine placenta is in concert with an inhibited expression of ras oncogenes. The results indicate that primary processing is blocked in case of Ha-ras, while a lower transcription rate or a stimulated degradation of mRNA is more likely for N-ras. These reactions are preceded by a specific binding of the inhibitor to tumor cell surface membranes. A modulated phosphate incorporation into some of the surface components is observed as a result of the binding process.

Expression of myc and ras oncogenes in two newly established neuroblastoma cell lines.

Two new neuroblastoma cell lines, KG-MH and KM-YH have been established from fresh tumour samples. In vitro growth characteristics are presented together with a karyological analysis. Northern and Southern blot experiments have been performed using molecularly cloned probes for c-myc, N-myc, c-Ha-ras, c-Ki-ras, and N-ras oncogenes. Both cell lines showed expression for N-myc, while c-myc expression was not detected. Cell line KM-YH, with a rather long population doubling time of 78 h, showed additional expression for the three ras genes.

Aminoacylase-1 isoenzymes: a comparative study.

Analysis of aminoacylase-1 (ACY-1) zymograms from 21 species indicated one structural locus coding for one dimeric enzyme. Among the various strains of five laboratory mammals (Mesocricetus auratus, Cricetulus griseus, Mus musculus, Rattus norvegicus, Cavia porcellus) only in Mus musculus-strains genetic variability was found. Crosses segregating for ACY-1b/ACY-1c reveal a three-banded banding pattern typical for the heterozygous state of a dimeric enzyme. Electrophoretic comparisons of all species studied indicate a high degree of phylogenetic variability at this locus.

Molecular cloning and characterization of the MET6 gene of Saccharomyces cerevisiae.

A yeast DNA fragment complementing the met6 mutation in yeast (Saccharomyces cerevisiae) was cloned in a shuttle vector, Yep13, by transforming a yeast host with plasmid DNA prepared from yeast gene bank CV13 of K. Nasmyth. A restriction map of a 6-kb Sau3A insert was constructed. A 2.6-kb fragment (Sau3A-BamHI) complementing the mutation was found by subcloning. Evidence that the DNA fragment contains the yeast MET6 gene was obtained by genomic integration. A 2.5-kb transcript is found both in wild-type (wt) and met6 yeast strains by Northern blotting experiments, indicating that the mutation acts at posttranscriptional level. The rate of transcription for the integrant lies between the values observed for the wt and mutant strains. The functional gene product seems to be involved in negative regulation of transcription of the MET6 gene.