8 Genetic Analysis of Retroviral Reverse Transcriptase Structure and Function

Abstract

Central to their life cycle, the process of reverse transcription in retroviruses comprises (1) the copying of genetic information present in the viral RNA genome to produce a double-stranded DNA and (2) the rearrangement of viral transcriptional elements and genes into an order that produces a viral DNA poised for expression upon chromosomal integration (Weiss et al. 1984; Goff 1990). The reverse transcriptase (RT) enzyme is a complex and multifunctional machine that is responsible for single-handedly carrying out all of the steps in the process. Genetic approaches to understanding the structure and function of this enzyme have been exceedingly fruitful in yielding information about the organization of the active domains, the residues needed for its various activities, and the interdependencies displayed by its domains. This chapter discusses the results of these genetic studies, first for several RTs in general and then in considerable detail for the human immunodeficiency virus type-1 (HIV-1) RT.

The crucial role played by RT in viral replication has made it an attractive target for antiviral therapy for human retroviruses such as HIV, the causative agent of AIDS (Chandra et al. 1985; Mitsuya and Broder 1987; Mitsuya et al. 1990), and human T-lymphotropic virus type I (HTLV-I), the agent of adult T-cell leukemia (ATL). To further our knowledge of molecular events during retroviral DNA synthesis, it is essential to understand the architecture and functional organization of the RT molecule. Studies aimed at unraveling the structural features of RT should therefore reveal fundamental aspects of this class of...