Notes on Genus: Alpharetrovirus

enveloped spheres

Type member: Avian leukosis virus

Contents

Members of this Genus General Description Morphology Electron Micrograph Genome Genus Genomic Organization Genome Map Type Member Genomic Organization Curated Sequences

General Description

This is one of the genera in the family Retroviridae. Fully-functional members are distinguished from those of the other genera by the presence of only 4 ORFs and a genome of less than 8 kb. Some species incorporate oncogenes and others are replication defective, with variable deletions in the gag, pol and env genes.

Morphology

Virions are spherical and enveloped, 80-100 nm in diameter, with suface projections of glycoprotein.

Genome

A dimer of linear, positive sense, ssRNA molecules, each about 7 kb long (without any oncogene) and with a 3'-polyA tail.

Genus Genomic Organization

Fully functional species contain 4 genes (gag, pro, pol and env) which are cleaved into the mature proteins. A spliced mRNA is used to generate the env and frameshifting is used in the generation of the pol.

Type Member Genomic Organization

The four major genes are

1. gag: structural polyprotein of 74.6 kDa
2. pro: protease of 13.6 kDa
3. pol: polyprotein of 98.6 kDa containing the reverse transcriptase (RT, 62.9 kDa) and integrase (IN, 35.7 kDa)
4. env: envelope proteins, consisting of surface protein (SU, 37.2 kDa) and transmembrane protein (TM, 22.3 kDa)

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