TRANSCRIPTION STIMULATION BY ADENOVIRUS E1A PROTEIN

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Adenovirus E1A protein is directly involved in oncogenic transformation by adenovirus. It is a nuclear protein with structural and functional homology to the product of the important human oncogene c-myc. Expression of E1A protein results in a great stimulation of the transcription of genes introduced into mammalian cells by transfection or viral infection. The molecular mechanism of E1A protein function is not known. Recently we have made a breakthrough in determining the mechanism of transcription induction by E1A protein. We found that expression of E1A protein greatly stimulates the transcription of genes transcribed by RNA polymerase III as well as RNA polymerase II. Of great practical significance, this increased transcriptional activity observed in vivo is also observed in vitro with extracts prepared from adenovirus infected and transformed cells. This is the first time an E1A protein-induced increase in transcriptional activity has been observed in vitro. It opens the door to enzymological, protein fractionation and purification studies which should be very informative. Preliminary results indicate that E1A protein does not stimulate in vitro transcription directly. Rather, its expression in vivo leads to an increase in the activity of the limiting transcription factor required for the formation of RNA polymerase III pre-initiation complexes, TF IIIC. We propose to continue these enzymological studies to confirm that expression of E1A protein does increase TF IIIC activity, and if it does, to determine the mechanism by which it does. Functional assays for TF IIIC is increased as a result of E1A expression, or if post-translational modifications of TF IIIC are induced which increase its specific activity. Based on these results, we also propose to determine the affect of E1A protein on the activity of transcription factors required for transcription by RNA polymerase II. These studies may suggest a biochemical activity for E1A protein, and hence for a nuclear transforming protein.