The potential for homeostatic regulation of the X region proteins of the human T cell leukemia virus type I.

The human T cell leukemia/lymphoma virus type I (HTLV-I) encodes two regulatory proteins, a 42 kDa trans-activator protein (p42tax) and a 27 kDa protein (p27rex), required for virus capsid protein synthesis. The experiments described here show that the p27rex protein negatively regulates the expression of the p42tax protein by suppressing the accumulation of the spliced messenger RNA from which the p42tax and p27rex proteins are made. It is proposed that such an interplay between the two regulatory genes results in a homeostatic system that may regulate the rate of viral replication as well as the growth of HTLV-I transformed cells.