The putative zinc finger of a caulimovirus is essential for infectivity but does not influence gene expression.
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
Plant pararetroviruses, such as caulimoviruses, and animal retroviruses have in common the presence of a highly conserved arrangement of cysteines and a histidine in the precursor of the capsid protein. The composition of these amino acids resembles a zinc finger element, a structure that is common to a class of eukaryotic proteins that regulate gene expression. The role of the putative zinc finger in the life-cycle of caulimoviruses was investigated by introducing specific mutations in the coat protein coding region of a cloned and infectious form of figwort mosaic virus, a caulimovirus. This mutated viral genome, which no longer encoded the conserved cysteine and histidine residues, was not infectious in plants. Transient expression assays in protoplasts showed that expression of a reporter gene inserted at different places in the genome was not detectably influenced by the coat protein or its putative zinc finger. It appears that the zinc finger-like element of caulimoviruses is not involved in the regulation of gene expression. These observations support a model which predicts a function of the zinc finger in specific recognition and packaging of viral RNA into virions prior to reverse transcription.