Livia Cioe

Inhibition of animal virus production by means of translation inhibitors unable to penetrate normal cells

Abstract The correlation between virus and host protein synthesis, membrane leakiness, and virus production has been studied in vesicular stomatitis virus-infected L cells, herpes simplex virus (type 1)- and Sendai virus-infected 37RC cells. In all three systems, membrane leakiness, as measured by an altered permeability to low-molecular-weight translation inhibitors (e.g., hygromycin B), is detectable at a time when the cells are very actively engaged in virus protein synthesis. The alteration of the membrane increases as the virus life cycle goes on so that an almost total and specific inhibition of viral translation by hygromycin B is achieved late in infection. Although the overall protein synthesis is not shut off in Sendai virus-infected cells, a gradual replacement of host protein synthesis by viral translation parallels an increasing plasma membrane permeability to hygromycin B, which is also correlated with the ever increasing fraction of infected cells. These results indicate that cells actively engaged in viral protein synthesis have lost, at least partially, the permeability barrier that plasma membrane maintains in uninfected cells. The presence of hygromycin B in the culture medium significantly reduces the production of mature virus in the three systems studied suggesting that this approach may prove useful in the search for antiviral agents.

Inhibition of adipose conversion of BALB/c 3T3 cells by interferon and 12-O-tetradecanoylphorbol-13-acetate

The adipose conversion of BALB/c 3T3 preadipose cells is inhibited by interferon; this inhibition is directly correlation with the interferon concentration. In cultures treated with low doses of interferon and the tumor promoter 12-O-tetradecanoylphorbol-13-acetate, another inhibitor of adipose conversion (Diamond et al., 1977), the two compounds act synergistically to block differentiation. Several lines of evidence suggest that the compounds differ in the mechanism by which they inhibit adipose conversion.

Sequence comparison of human and murine erythrocyte alpha-spectrin cDNA

The results of hybridization analyses using cDNA probes for mouse and human alpha-spectrin mRNA indicate that a single gene encodes the alpha-subunit of erythrocyte spectrin. Sequencing of the cDNA clones showed that they code for 370 amino acids (aa) covering three repeat domains close to the C terminus of alpha-spectrin. The cloned cDNAs will now permit the isolation of the alpha-spectrin gene and should lead to the characterization of the genetic aspects in human hereditary anemias in which alpha-spectrin has been characterized as the site of the molecular defect.

Cloning of rabies virus matrix protein mRNA and determination of its amino acid sequence

A cDNA clone of mRNA for rabies virus matrix (M) protein has been identified. The clone hybridizes to an mRNA species from rabies virus-infected cells, whose size correlates to the size of the M protein in rabies virions, and selects an mRNA that translates into a polypeptide corresponding in size to M protein. The nucleotide sequence of the cloned cDNA was determined and from this a complete amino acid sequence for M protein was deduced. The deduced sequence of 202 amino acids bears no detectable sequence homology with vesicular stomatitis virus M protein although these proteins may share functional homology.

Assignment of mouse beta-spectrin gene to chromosome 12

The structural gene for the Β-subunit of the mouse erythrocyte spectrin, hereinafter designated as Sp-b, was assigned to the mouse chromosome 12. This assignment was made by Southern analysis of genomic DNA from mouse X Chinese hamster hybrid cells using cloned mouse erythrocyte Β-spectrin cDNA as a probe. In the PstI-digested genomic hamster cell DNA a single band of 2.0 kb was detected, whereas PstI-digested mouse DNA gave a band of 4.2 kb, when probed with the mouse erythroid Β-spectrin cDNA clone. This allowed us to analyze a panel of mouse X Chinese hamster somatic cell hybrids to map this gene to chromosome 12. Interestingly, this assignment is different from that observed for the α-subunit of spectrin, which has been mapped to chromosome 1 in mouse. These results serve as a basis for further genetic characterization of the mouse hemolytic anemias.

Effects of a chromatin low molecular weight peptidic fraction on differentiation markers and virus production in Friend leukemia cells.

Low molecular weight chromatin peptides exert a dose-dependent inhibition of Dimethylsulfoxide (DMSO)-induced erythroid differentiation of murine Friend Leukemia Cells (FLC). This effect correlates with the degree of purification of the peptide fractions. Crot analysis of globin mRNA amounts in DMSO-treated FLC given the peptides showed a 4-5-fold decrease of messenger RNA in the cytoplasm with no nuclear storage of globin transcripts. Spectrin accumulation in “induced” FLC is inhibited as well. The effects of the peptides on erythroid markers are reversible upon removal of the compounds. They also appear to bespecific forinduced gene expression as (1) no effects are observed on cell growth and RNA synthesis in normalnondifferentiating cell lines; and (2) no changes have been detected with regard to the expression of integrated viral genes coding for continuous shedding of viral particles.