Selection and characterization of interferon response mutants from mouse L929 fibroblast cells

Interferon (IFN) response mutants were selected from mouse L929 fibroblast cells and their specific resistance to is-1, an IFN-sensitive mutant of mengovirus, was studied. The standard L cell subline used in our laboratory (G3), is resistant to is-1 infection after pretreatment with low levels of IFN. Two clonal sublines that support the growth of is-1 in the presence of IFN (AS-4 and TA-6) were isolated from it, and two revertant lines (AS-4R1 and TA-6R1) were subsequently selected from AS-4 and TA-6. The kinetics of is-1 growth in the presence of IFN were found to vary in each of these sublines. Specific resistance to is-1 cannot be accounted for by enhanced induction of IFN, ability to bind IFN, or increased 2'-5'-oligo(A)-dependent endonuclease activity. AS-4 and TA-6 appear to have arisen through loss of one or more whole chromosomes. The origin of TA-6R1 is unclear.