G. C. Sen

Increased endonuclease activity in an extract from mouse Ehrlich ascites tumor cells which had been treated with a partially purified interferon preparation: Dependence on double-stranded RNA

Summary Reovirus messenger RNAs are degraded faster in crude extracts (S30) from mouse Ehrlich ascites tumor cells which have been treated with either a partially purified interferon preparation or the interferon inducer poly(I)·poly(C) than in corresponding extracts from untreated cells. The faster degradation appears to be a consequence of endonuclease action. The endonuclease activity in vitro depends on the presence of double-stranded reo-virus RNA in the reaction mixture.

Interferon, double-stranded RNA and RNA degradation. Fractionation of the endonucleaseINT system into two macromolecular components; Role of a small molecule in nuclease activation

Abstract We reported earlier that a) the incubation of an extract from interferon-treated Ehrlich ascites tumor cells with double-straded RNA and ATP results in the activation of an endonuclease and b) after the activation the double-stranded RNA and ATP can be degraded without impairing the activity of the endonuclease. We report now the separation and partial purification of two macromolecular components (DE1 INT and DE2 INT ) involved in the process. Upon incubation with double-stranded RNA and ATP component DE1 INT generates a heat-stable product of low molecular weight (designated as nuclease activator). On incubation with the nuclease activator a latent nuclease in component DE2 INT is activated.

Inhibition of reovirus messenger RNA methylation in extracts of interferon-treated ehrlich ascites tumor cells

Summary The methylation of (unmethylated) reovirus mRNA is impaired in extracts of interferon-treated Ehrlich ascites tumor cells. The impairment is due to one or more inhibitors. Its extent decreases with an increasing concentration of reovirus mRNA in the reaction mixture. The impairment is apparently not a consequence of the degradation of reovirus mRNA. Since methylation of reovirus mRNA is apparently required for translation, it is conceivable that the impairment of methylation may be part of the antiviral activities of interferons.

Interferon-associated, dsRNA-dependent enzyme activities in a mutant 3T6 cell engaged in the semiconstitutive synthesis of interferon

Cytoplasmic extracts of untreated cultures of a virus-resistant mutant of mouse 3T6 cells, designated 3T6-VrB2, contain two double-stranded, RNA-activated enzyme activities associated with interferon action. These are the synthesis of a low molecular weight oligonucleotide inhibitor of cell-free protein synthesis from ATP, and the phosphorylation of a 67,000 dalton polypeptide by transfer of the gamma phosphate of ATP. Basal levels of both enzyme activities are detectable in extracts of untreated parental 3T6 cells, and are greatly enhanced upon interferon pretreatment. A procedure was developed, using a nonionic detergent to effect cell lysis, which allowed the analysis of the protein kinase activity from as few as 2 x 10(7) cells. Using this procedure, direct proportionalities were demonstrated between the concentration of interferon to which 3T6 cells were exposed, and both the level of protein kinase activity and the magnitude of the antiviral state were established in these cells. Furthermore, untreated cultures of 3T6-VrB2 exhibited both an antiviral state and an intracellular protein kinase activity equal to that of cultures of the parental 3T6 cells pretreated with a single concentration of mouse interferon.