Secretory proteins induced in human fibroblasts under conditions used for the production of interferon beta.

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Abstract
Human fibroblast cells treated with a combination of inhibitors of protein and RNA synthesis [cycloheximide and actinomycin D as used to superinduce interferon .beta. (IFN-.beta.)] secrete 2 proteins with MW of 22,000 and 27,000 kilodaltons (22-kDal and 27-kDal) that are precipitable with an antiserum raised against impure IFN-.beta. but are antigenically distinct from IFN-.beta.1. Translation in vitro of mRNA extracted from human fibroblast cells induced for the production of IFN-.beta. leads to the synthesis of a 26-kDal protein that is structurally closely related to the 22- and 27-kDal proteins. This 26-kDal protein mRNA is relatively abundant and also appears in human fibroblasts induced only with cycloheximide. It has been partially purified by sucrose gradient centrifugation and more extensively by diazobenzyloxymethyl-cellulose hybridization to plasmid DNA from a bacterial c[complementary]DNA clone. When translated in an in vitro reticulocyte system supplemented with dog pancreas microsomes, the 26-kDal protein and 2 other intermediates corresponding presumably to its signal-cleaved (19-kDal) and partially glycosylated (24-kDal) forms were observed. Crude, partially purified, and highly purified 26-kDal mRNA failed to program the synthesis of antiviral or ppp(A2''p5'')nA synthetase-inducing activity when translated in Xenopus laevis oocytes. Partially purified 22-kDal and 27-kDal (i.e., the in vivo equivalents of the 26-kDal protein) are also devoid of antiviral or ppp(A2''p5'')nA synthetase-inducing activity. Hence, this 26-kDal mRNA, although presumably identical to the human IFN-.beta.2 mRNA, cannot be considered to be a fibroblast interferon mRNA.