6 Protein Biosynthesis and Assembly

Abstract

I. INTRODUCTION
To understand the transmission of viruses, a knowledge of the events that enable the viral genome to replicate, produce structural components, and become packaged into virions is required. The organization of retroviral genomes and the mechanisms involved in their replication are discussed in the preceding two chapters. Here, we describe how the genome-encoded instructions are processed by the cell to allow the accumulation of virus-specific products and how these products become associated to produce new viral particles.

Before proceeding to a discussion of the biosynthesis of retroviral proteins, we will compare retroviruses with other virus groups in a general way and discuss techniques used to study the mature viral proteins and their precursors. Following this, the characteristics shared among the different retrovirus subfamilies will be summarized. Finally, the composition and structures of virion components and the mechanisms involved in generating mature virions will be described separately and in considerable detail for some of the major retrovirus groups.

A. Comparative Strategies for Viral Protein Synthesis
Viruses use a variety of stratagems to process their genetic information into specialized enzyme activities or new structural components. This section contrasts the mechanisms used by several virus groups and compares them with those used by retroviruses.

An important feature of eukaryotic cells, relevant to the strategy of viral gene expression, is the apparent inability of eukaryotic translation systems to use more than one initiation site per mRNA molecule. Thus, unlike prokaryotic systems, eukaryotic cells synthesize only one type of polypeptide chain per mRNA...