Deng W, Chen L, Wood D W, Metcalfe T, Liang X, Gordon M P, Comai L, Nester E W
Department of Microbiology, Box 357242, University of Washington, Seattle, WA 98195-7242, USA.
Proc Natl Acad Sci U S A. 1998 Jun 9;95(12):7040-5. doi: 10.1073/pnas.95.12.7040.
Agrobacterium tumefaciens induces crown gall tumors on plants by transferring a nucleoprotein complex, the T-complex, from the bacterium to the plant cell. The T-complex consists of T-DNA, a single-stranded DNA segment of the tumor-inducing plasmid, VirD2, an endonuclease covalently bound to the 5' end of the T-DNA, and perhaps VirE2, a single-stranded DNA binding protein. The yeast two-hybrid system was used to screen for proteins interacting with VirD2 and VirE2 to identify components in Arabidopsis thaliana that interact with the T-complex. Three VirD2- and two VirE2-interacting proteins were identified. Here we characterize the interactions of VirD2 with two isoforms of Arabidopsis cyclophilins identified by using this analysis. The VirD2 domain interacting with the cyclophilins is distinct from the endonuclease, omega, and the nuclear localization signal domains. The VirD2-cyclophilin interaction is disrupted in vitro by cyclosporin A, which also inhibits Agrobacterium-mediated transformation of Arabidopsis and tobacco. These data strongly suggest that host cyclophilins play a role in T-DNA transfer.
根癌土壤杆菌通过将一种核蛋白复合体——T复合体从细菌转移到植物细胞，从而在植物上诱发冠瘿瘤。T复合体由T-DNA（肿瘤诱导质粒的单链DNA片段）、共价结合在T-DNA 5'端的核酸内切酶VirD2以及可能还有单链DNA结合蛋白VirE2组成。利用酵母双杂交系统筛选与VirD2和VirE2相互作用的蛋白质，以鉴定拟南芥中与T复合体相互作用的成分。鉴定出了三种与VirD2相互作用的蛋白和两种与VirE2相互作用的蛋白。在此，我们描述了通过该分析鉴定出的VirD2与拟南芥亲环蛋白的两种同工型之间的相互作用。与亲环蛋白相互作用的VirD2结构域不同于核酸内切酶结构域、ω结构域和核定位信号结构域。环孢菌素A在体外破坏VirD2-亲环蛋白的相互作用，环孢菌素A也抑制根癌土壤杆菌介导的拟南芥和烟草的转化。这些数据有力地表明宿主亲环蛋白在T-DNA转移中起作用。
