Regulation of Gene Expression by Oncoproteins
There are several examples, where oncoproteins regulate gene expression : (i) C-erb A oncogene of AEV codes for a protein that resembles a steroid receptor and may thus regulate gene expression; (ii) c-jun gene related to v-jun of ASV-17, codes for the transcription factor API or a part of it. AP-1 acts at enhancers and stimulates their activity. Actually fos and jun proteins form a complex that binds to DNA at the TGACTCA box and work together as a transcription factor of some significance.

E1A is another oncoprotein (phosphoprotein located in the nucleus), which regulates gene expression by interacting with several other cellular proteins. This protein activates expression of some genes and represses the activity of some other genes. It is capable of giving rise to three transcripts due to alternative splicing of the primary transcript.