Moore S P, Rinckel L A, Garfinkel D J
ABL-Basic Research Program, NCI-Frederick Cancer Research and Development Center, Maryland 21702-1201, USA.
Mol Cell Biol. 1998 Feb;18(2):1105-14. doi: 10.1128/MCB.18.2.1105.
Ty1 retrotransposition in Saccharomyces cerevisiae requires integrase (IN)-mediated insertion of Ty1 cDNA into the host genome. The transposition components are assembled in the cytoplasm and must cross the nuclear envelope to reach the genomic target, since, unlike animal cell nuclear membranes, the yeast cell nuclear membrane remains intact throughout the cell cycle. We have identified a bipartite nuclear localization signal (NLS) in IN required for Ty1 transposition (Ty1 IN) that directs IN to the nucleus. Mutations in the NLS that specifically abolish nuclear localization inactivate transpositional integration but do not affect reverse transcription, protein processing, or catalytic activity in vitro. No additional Ty1-encoded proteins are required for IN nuclear localization. Intragenic complementation experiments suggest that Ty1 IN functions as a multimer and contains two distinct domains, one required for integration and the other for nuclear localization. Nuclear targeting of the preintegration complex by an IN NLS may prove to be a general strategy used by retrotransposons and retroviruses that infect nondividing cells.
酿酒酵母中的Ty1逆转录转座需要整合酶（IN）介导将Ty1 cDNA插入宿主基因组。转座组件在细胞质中组装，并且必须穿过核膜才能到达基因组靶点，因为与动物细胞核膜不同，酵母细胞核膜在整个细胞周期中都保持完整。我们在Ty1转座所需的IN（Ty1 IN）中鉴定出一个双分型核定位信号（NLS），该信号将IN导向细胞核。NLS中特异性消除核定位的突变会使转座整合失活，但不影响体外逆转录、蛋白质加工或催化活性。IN的核定位不需要额外的Ty1编码蛋白。基因内互补实验表明，Ty1 IN作为多聚体发挥作用，包含两个不同的结构域，一个用于整合，另一个用于核定位。由IN NLS对整合前复合物进行核靶向可能是感染非分裂细胞的逆转录转座子和逆转录病毒所采用的一种通用策略。
