TUMOR-SUPPRESSOR GENES - NEWS ABOUT THE INTERFERON CONNECTION

The interferons are a family of secreted, multifunctional proteins whi ch are components of the defenses of vertebrates against viral, bacter ial, and parasitic infections and certain tumors. They exert their var ious activities by inducing the synthesis of a large variety of protei ns. There are direct and indirect indications that several of these pr oteins may have tumor-suppressor activities. The interferon-inducible proteins implicated include: (i) a double-stranded RNA-activatable pro tein kinase that can phosphorylate and thereby inactivate the eukaryot ic peptide chain initiation factor eIF-2; (ii) the interferon regulato ry factors IRF-1 and IRF-2, which can modulate the expression of the i nterferons and of some interferon-inducible proteins; and (iii) RNase L, a latent endoribonuclease which can be activated by (2'-5')oligoade nylates, the products of a family of enzymes which are also interferon -inducible. It is noteworthy that some of the proteins encoded by tumo r virus oncogenes (e.g., E1A from adenovirus, EBNA-2 from Epstein-Barr virus, and terminal protein from hepatitis B virus) impair the induct ion of at least some proteins by interferons.