P. Ahlquist et al., PROTEIN-PROTEIN INTERACTIONS AND GLYCEROPHOSPHOLIPIDS IN BROMOVIRUS AND NODAVIRUS RNA REPLICATION, Archives of virology, 1994, pp. 135-145
The plant bromoviruses and animal nodaviruses are distinct groups of p
ositive strand RNA viruses that have proven to be useful models for RN
A replication studies. Bromoviruses encode two large proteins required
for RNA replication: 1a contains domains implicated in helicase and c
apping functions, and 2a contains a central polymerase-like domain. Us
ing immunoprecipitation and far-western blotting, we have now shown th
at 1a and 2a form a specific complex in vitro and have mapped the inte
racting domains. Molecular genetic data implicate the 1a-2a complex in
RNA replication and suggest that it supports coordinate action of the
putative helicase, polymerase, and capping domains. The locations of
the interacting 1a and 2a domains have implications for replication mo
dels and the evolution of virus genomes bearing homologous replication
genes in fused vs. divided forms. For the nodavirus Flock house virus
(FHV), a true RNA replicase has been isolated that carries out comple
te, highly active replication of added FHV RNA, producing newly synthe
sized positive strand RNA in predominantly ssRNA form. Positive strand
RNA synthesis in this FHV cell-free system is strongly dependent on t
he addition of any of several glycerophospholipids. Positive strand RN
A synthesis depends on the complete glycerophospholipid structure, inc
luding the polar head group and diacyl glycerol lipid portion, and is
strongly influenced by acyl chain length.