GENETIC-ANALYSIS OF ADENOVIRUS E1A - INDUCTION OF GENETIC INSTABILITYAND ALTERED CELL MORPHOLOGIC AND GROWTH-CHARACTERISTICS ARE SEGREGATABLE FUNCTIONS

Single multifunctional oncoproteins contribute to genomic instability development, but relationships between one or more oncoprotein-associa ted activities and genetic changes accompanying tumor cell progression are uncertain. Using NIH 3T3 derivative EN/NIH 2-20 containing transc riptionally silent neomycin phosphotransferase gene (neo) integrants w ith undetectable spontaneous reactivations, we studied wild-type (WT) and mutant adenovirus E1A-induced neo reactivation by neo-allelic rear rangement. WT E1A expression, yielding differential splice transcripts 12S and 13S and resulting in altered cell, morphologic and growth cha racteristics, produced neo reactivations in 9 of 21 subclones (median rate per cell, 35 X 10(-6); range, 0.33 X 10(-6) to 936 x 10(-6)). Onl y 3 of 17 cell lines expressing CTd1976, a '12S' functional equivalent inducing altered cell morphologic and growth characteristics while la cking the 13S trans activation domain, yielded neo reactivations (rang e, 0.33 X 10(-6) to 0.67 x 10(-6)). One of 21 subclones expressing NTd 1646, an E1A mutant retaining the trans domain but lacking p300 bindin g activity and the ability to alter cell morphologic and growth charac teristics, produced neo reactivations (8.7 x 10(-6)). Other E1A mutant s, all lacking the ability to alter cell morphologic and growth charac teristics while binding pRb but variously lacking the trans domain and binding for p107 and/or p300, displayed undetectable neo-reactivation s. 98 EN/NIH 2-20 derivatives coexpressing complementary mutant E1As e xhibited altered morphologic and growth features, but only 10 of these produced neo reactivations, and maximum rates (14 X 10(-6)) were subs tantially lower than those in comparably derived, morphologically alte red E1AWT-expressing counterparts (497 X 10(-6)). These findings sugge st that maximum rates of gene reactivations by genomic rearrangement r equire the collective activities of functional domains assembled in si ngle multifunctional proteins (or complexes) while altered cell morpho logic and growth characteristics may arise through comparable sets of functional domains distributed across more than one protein (or comple x). (C) 1998 Elsevier Science B.V. All rights reserved.