Use of CH3HgOH-agarose gels for the electrophoresis of heterogeneous nuclear RNA and messenger RNA from mammalian cells

Sequence of cDNA for rat cystathionine gamma-lyase and comparison of deduced amino acid sequence with related Escherichia coli enzymes

A cDNA clone for cystathionine gamma-lyase was isolated from a rat cDNA library in lambda gt11 by screening with a monospecific antiserum. The identity of this clone, containing 600 bp proximal to the 3'-end of the gene, was confirmed by positive hybridization selection. Northern-blot hybridization showed the expected higher abundance of the corresponding mRNA in liver than in brain. Two further cDNA clones from a plasmid pcD library were isolated by colony hybridization with the first clone and were found to contain inserts of 1600 and 1850 bp. One of these was confirmed as encoding cystathionine gamma-lyase by hybridization with two independent pools of oligodeoxynucleotides corresponding to partial amino acid sequence information for cystathionine gamma-lyase. The other clone (estimated to represent all but 8% of the 5'-end of the mRNA) was sequenced and its deduced amino acid sequence showed similarity to those of the Escherichia coli enzymes cystathionine beta-lyase and cystathionine gamma-synthase throughout its length, especially to that of the latter.

A review of the toxicity of methylmercury compounds with application to occupational exposures associated with laboratory uses

The toxicological and physicochemical properties of methylmercury compounds are reviewed together in an attempt to foster a conceptual synthesis between the biochemistry and toxicity of these compounds. Where insights from chemical analysis bear on conclusions derivable from earlier toxicology studies, these studies have in some instances been reinterpreted. Physical and toxicity data alike are relevant to evaluating risk, and an application of these principles is made to assess occupational exposures in the particular setting of the laboratory. Information is presented from which hazard evaluation may be extrapolated to include a wide range of other exposure environments.

Physical parameters affecting the rate and completion of RNA driven hybridization of DNA: new measurements relevant to quantitation based on kinetics

Differences in the RNA-driven hybridization kinetics of genomic DNA and cDNA probes led us to examine physical parameters affecting these reactions. Cloned cDNA complementary to serum albumin (SA) mRNA hybridized in accordance with single component kinetics, whereas cloned SA genomic DNA hybridized more slowly and with multiple component kinetics. This difference is largely attributable to the relatively short and variable lengths of the mRNA complementary regions in the cloned genomic DNA. The rate of mRNA driven hybridization is affected to about half the extent observed for DNA renaturation as Na+ is increased or decreased from 0.18M. In the annealing of nucleic acids of high sequence complexity, after approximately 70% of reaction has been reached, the rate of the reaction is slowed and completion is not reached under "static" conditions. In practical terms, this is not the case for systems of low sequence complexity. This problem can be largely overcome by continuous or frequent mixing of the reactants, so that complex cDNA probes are hybridized essentially to completion, and kinetics can therefore be more readily compared to simple complexity standards.

Sequence complexity and diversity of polyadenylated RNA molecules of human normal resting, PHA-stimulated and leukemic lymphocytes

The abundance and complexity of total poly(A)+RNA of human normal unstimulated lymphocytes, PHA-stimulated and leukemic lymphocytes were examined using the cDNA-poly(A)+ RNA hybridization technique. It was found that in both PHA-stimulated and leukemic lymphocytes the complexity of total poly(A)+RNA is strongly reduced in respect to normal unstimulated lymphocytes. The differences is due to a small portion, by weight, of high complexity sequences, suggesting the involvement or nuclear, not necessarily transcriptional, events. Moreover the heterologous hybridizations show that: 1) in PHA-stimulated lymphocytes there is a set of highly abundant sequences which are represented in normal and leukemic lymphocytes at a very reduced rate; 2) the sequences abundant in normal unstimulated lymphocytes are less represented in leukemic lymphocytes; the converse also is true, but at a lower extent. On the basis of available data, it is suggested that the observed changes in the abundance pattern of PHA-stimulated lymphocytes may be related mainly to a difference in the half-life of the mRNAs, while those of leukemic lymphocytes require some transcriptional or post-transcriptional nuclear event.

Heterogeneity of poly(I) x poly(C)-induced human fibroblast interferon mRNA species

Three classes of human interferons (IFNs) have been defined on the basis of their immunological properties: the 'Le' or 'alpha' IFN, mainly derived from leukocyte or lymphoblastoid cells; the 'F' or 'beta' IFN, mainly derived from fibroblast cultures; and the 'T', 'immune' or 'gamma' IFN, mainly derived from mitogen- or antigen-stimulated lymphoid cells. Whereas several individual species of Le IFN have been purified to homogeneity, it is generally considered that F IFN represents a single protein. Thus current efforts to clone human fibroblast IFN mRNA sequences are based on the observation that F IFN mRNA sediments in sucrose gradients as a single RNA species of size corresponding to 12-14 S (refs 7-10). We show here, using gel electrohporesis of mRNA, that two populations of translationally active human fibroblast IFN mRNA molecules exist--an abundant '14 S' species and a scarce '11 S' species. Microinjection of either species of mRNA into Xenopus oocytes leads to the synthesis of biologically active F-type human IFN. These data agree with and complement recent RNA hybridization studies of Weissenbach et al.