Jr. Zupan et al., AGROBACTERIUM VIRE2 PROTEIN MEDIATES NUCLEAR UPTAKE OF SINGLE-STRANDED-DNA IN PLANT-CELLS, Proceedings of the National Academy of Sciences of the United Statesof America, 93(6), 1996, pp. 2392-2397
Agrobacterium genetically transforms plant cells by transferring a sin
gle-stranded DNA (ssDNA) copy of the transferred DNA (T-DNA) element,
the T-strand, in a complex with Agrobacterium proteins VirD2, bound to
the 5' end, and VirE2, VirE2 binds single-stranded nucleic acid coope
ratively, fully coating the T-strand, and the protein localizes to the
plant cell nucleus when transiently expressed. The coupling of ssDNA
binding and nuclear localizing activities suggests that VirE2 alone co
uld mediate nuclear localization of ssDNA, In this study, fluorescentl
y labeled ssDNA accumulated in the plant cell nucleus specifically whe
n microinjected as a complex with VirE2, Microinjected ssDNA alone rem
ained cytoplasmic. Import of VirE2-ssDNA complex into the nucleus via
a protein import pathway was supported by (i) the inhibition of VirE2-
ssDNA complex import in the presence of wheat germ agglutinin or a non
hydrolyzable GTP analog, both known inhibitors of protein nuclear impo
rt, and (ii) the retardation of import when complexes were prepared fr
om a VirE2 mutant impaired in ssDNA binding and nuclear import.