The E1a gene of adenovirus encodes two proteins, 289 and 243 amino acids long, 
which have positive (transactivator) and negative (enhancer repressor) RNA 
polymerase II transcriptional regulatory properties and cell transformation 
activities including cooperation with an activated ras gene. The E1a 
transforming functions more closely correlate with the repressor property than 
with transactivation in that both E1a proteins express the repressor and 
transformation functions while only the 289-amino-acid protein is an efficient 
transactivator. To understand whether the transcriptional regulatory activities 
of E1a are related to its ras cooperation activity, we generated a series of 
mutant E1a expression vectors by linker insertion mutagenesis of the 
289-amino-acid protein. Here we describe a new class of mutants which although 
defective for enhancer repression still can cooperate with the ras oncogene in 
cell transformation. The mutants are also defective in transcription 
transactivation. Our data suggest that enhancer repression and transformation 
via ras cooperation are separate E1a functions and that cooperation with ras 
does not rely on either of the RNA polymerase II transcription regulatory 
functions of E1a. We also show that mutations which inactivate enhancer 
repression are not confirmed to a single critical domain necessary for 
repression. We therefore propose that the integrity of the overall configuration 
of the E1a proteins is important for the repression activity.