The definition of a large viral transcription unit late in Ad2 infection of HeLa cells: mapping by effects of ultraviolet irradiation.

The synthesis of Ad2-specific nuclear RNA in HeLa cells 15 hr post-infection has been examined after ultraviolet irradiation. The synthesis of RNA complementary to various segments of Ad2 DNA is decreased differentially, with the most sensitive region at the right end of the physical map and the most resistant in the region from 0 up to 0.2-0.3 (20-30% from the left end of the genome). For a given ultraviolet dose, the amount of labeled RNA homologous to various DNA fragments decreased exponentially from map position 0.2-0.3 to 1.0. These results suggest that a major transcriptional unit late in Ad2 infection is a rightward-transcribing unit between 0.0-0.3 and 1.0.