28 Parvovirus DNA Replication

Abstract

Parvoviruses are unique among all known viruses in having single-stranded DNA genomes which are linear. Virions are non-enveloped, containing a single copy of the small (4–6 kb) viral chromosome encapsidated in a rugged icosahedral protein capsid 18–26 nm in diameter. Although lacking associated enzymes or nucleosomal proteins, the particles have been shown, in some cases, to contain polyamines such as spermidine, spermine, and putrescine (Berns et al. 1995). The family Parvoviridae contains a broad spectrum of physically similar viruses that replicate in the nuclei of both invertebrate and vertebrate hosts. Viruses infecting mammalian cells form the subfamily Parvovirinae and include a number of helper-independent viruses, represented in this review by minute virus of mice (MVM), and the adeno-associated (AAV) viruses, represented here by AAV2, which, in general, only replicate in cells coinfected with a helper adenovirus or herpes virus. Further background information on the structure and biology of the parvoviruses can be obtained from reviews published elsewhere (Cotmore and Tattersall 1987; Berns 1990, 1995; Tjissen 1990; Muzyczka 1992). Space constraints allow only a representative selection of the most directly pertinent references to be cited herein.

Whereas AAV encapsidates, in separate virions, DNA strands of either sense, MVM selectively encapsidates (to 99%) strands that are minus sense with respect to transcription. Both viruses encode all of their known proteins from a single-sense DNA strand, and each encodes two separate gene complexes. Transcripts from one half of the genome, designated by convention the right-hand side, program synthesis of an overlapping...