The putative zinc finger of a caulimovirus is essential for infectivity but does not influence gene expression.
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.
Scholthof
H B
HB
Department of Plant Pathology, University of Kentucky, Lexington 40546.
Wu
F C
FC
Kiernan
J M
JM
Shepherd
R J
RJ
D000595:Amino Acid Sequence; D002213:Capsid / Q000737:chemistry / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D008969:Molecular Sequence Data; D010942:Plant Viruses / Q000235:genetics / Q000254:growth & development*; D012333:RNA, Messenger / Q000235:genetics; D012191:Retroviridae Proteins / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*; D014779:Virus Replication; D016335:Zinc Fingers
D012333:RNA, Messenger; D012191:Retroviridae Proteins; D014764:Viral Proteins