AMPLIFICATION OF RECOMBINANT ADENOVIRAL TRANSGENE PRODUCTS OCCURS BY INHIBITION OF HISTONE DEACETYLASE

n-Butyrate (butyrate) has been shown to amplify transgene expression i n cells infected with El-defective adenoviruses. The present studies w ere undertaken in order to better define the actions of butyrate in th e context of adenovirus gene expression, and to attempt to elucidate t he mechanism by which butyrate mediates the transgene amplification. I t was found that butyrate amplified viral transgene expression over a concentration range of 0.5-5 mM, and that the amplification required a n exposure of 12-24 hr for maximal effect. Western blot analysis of re presentative viral proteins showed that butyrate treatment amplified D NA-binding protein, but not fiber protein. A transient adenoviral repl ication system suggested that butyrate had a modest inhibitory effect on replication of the El-defective adenovirus. Use of a specific inhib itor of histone deacetylase, trichostatin A (TSA), reproduced the ampl ification of the viral transgene product achieved with the butyrate. I n contrast, adenoviral transgene expression could not be amplified by TSA treatment in a cell line known to have a TSA-resistant histone dea cetylase. Butyrate amplified steady-state gene expression of the viral transgene, but had no detectable effects on either DNA-binding protei n or fiber steady-state gene expression. Nuclear run-off experiments s howed that both butyrate and TSA caused an increase in the viral trans gene transcription. It was concluded that inhibitors of histone deacet ylase amplify adenoviral transgene expression at the transcriptional l evel. (C) 1997 Academic Press.