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J. Virol., Feb 1996, 1173-1181, Vol 70, No. 2
N Pardigon and JH Strauss
We have isolated a 50-kDa mosquito protein that binds with high affinity to
a riboprobe representing the 3' end of the minus strand of Sindbis virus
RNA. The isolated protein has been used to obtain cDNA clones encoding this
protein that have been sequenced and used to express the protein in large
amounts. Sequence comparisons make clear that this protein is the mosquito
homolog of the La autoantigen. The N- terminal half of the protein shares
considerable sequence identity with the human La protein, the rat La
protein, and the recently identified Drosophila melanogaster homolog. There
is one stretch of 100 amino acids in the N-terminal domain in which 48
residues are identical in all four proteins. In contrast, the C-terminal
domain of the mosquito protein shares little identity with any of the other
three proteins. We have also shown that the mosquito protein, the human
protein, and a putative chicken homolog of the La protein cross-react
immunologically and, thus, all share antigenic epitopes. The mosquito La
protein is primarily nuclear in location, but significant amounts are
present in the cytoplasm, as is the case for the La proteins of other
species. The equilibrium constant for the binding of the expressed mosquito
La protein to the Sindbis virus riboprobe is 15.4 nM, and thus the affinity
of binding is high enough to be physiologically relevant. Furthermore, the
conservation of this protein in the animal kingdom may be significant,
because Sindbis virus utilizes mosquitoes, birds, and mammals as hosts. We
propose that the interactions we observe between the La protein and toes,
birds, and mammals as hosts. We propose that the interactions we observe
between the La protein and a putative promoter in the Sindbis virus genome
are significant for Sindbis virus RNA replication.
Copyright © 1996, American Society for Microbiology
Mosquito homolog of the La autoantigen binds to Sindbis virus RNA
Division of Biology, California Institute of Technology, Pasadena 91125, USA.
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