ABSTRACT
The study of retroviruses has proven to be a remarkably fruitful endeavor. Retroviruses are universally recognized as important human and animal pathogens, as valuable models for carcinogenesis, and as paradigms for a mechanism of information transfer that has apparently been a strong force in modeling eukaryotic genomes. The enhancer sequences can provide considerable biological specificity by affecting both the rate of virus replication as well as the cell specificity of replication and pathogenesis. Virions of retroviruses have a fairly simple protein composition, usually containing only eight or nine proteins. Infection with a number of retroviruses — including Human immunodeficiency virus (HIV) and even some oncoviruses — can lead to cell death in certain cell culture models. Two fundamentally different mechanisms have been proposed, both of which may be important in HIV infection. The integrated provirus behaves as though it were a cellular gene: it serves as an efficient template for mRNA synthesis by RNA polymerase II.
