Evidence that the Human Foamy Virus Genome Is DNA

Abstract

The genomes of the spumaviruses, of which human foamy virus (HFV) is the prototype, are very similar to those of other complex retroviruses. However, in some aspects of the viral replicative cycle, HFV more closely resembles pararetroviruses such as hepatitis B virus. Previous work indicated that HFV extracellular particles contain apparently full-length double-stranded DNA, as well as RNA. We have further characterized the amount of DNA in particles and the role that this DNA has in viral replication. Experiments with the reverse transcriptase inhibitor 3′-azido-3′-deoxythymidine (AZT) suggest that reverse transcription is largely complete before extracellular virus infects new cells. In addition, we have been able to show that DNA extracted from virions can lead to production of virus after transfection. Taken together, these data suggest that complete, or nearly complete, proviral-length DNA is present in viral particles and that this DNA is sufficient for new rounds of viral replication.

Viral Diseases of Nonhuman Primates

“…Foamy virus reverse transcription occurs during viral assembly or budding such that the process is complete before the virus infects new cells. Subsequently, the functional nucleic acid of SFV consists of double-stranded linear DNA rather than single-stranded RNA (Moebes et al, 1997;Yu et al, 1999). SFV also have two unique nonstructural proteins; Tas is a transcriptional activator, and Bet is involved in latency regulation.…”

Viral strategies of translation initiation: Ribosomal shunt and reinitiation

“…The members of Pararetrovirinae-also known as pararetroviruses---contain DNA in mature virions, in contrast to the RNA-containing retroviral virions. It is worth mentioning that virions of spumaviruses--a separate genus of Retrovirinae (or retroviruses)----can also contain DNA (54). This, together with other striking similarities to pararetroviruses (reviewed in Refs.…”

Oncogenic retroviruses in animals and humans

“…The genome is composed of 8-13 kB single-stranded RNA, resembling a cellular mRNA with (+) polarity, a cap structure at the 5k end and a poly-A tail at the 3k end. There is some evidence that spumaviruses do in fact use DNA as genetic material [20], but since they are not known to cause disease, we will not discuss this further. Simple retroviruses (e.g.…”