Merle E, Rose R C, LeRoux L, Moroianu J
Laboratory of Cell Biology, Biology Department, Boston College, Chestnut Hill, Massachusetts 02467, USA.
J Cell Biochem. 1999 Sep 15;74(4):628-37.
L1 major capsid proteins of human papillomaviruses (HPVs) enter the nuclei of host cells at two times during the viral life cycle: 1) after infection and 2) later during the productive phase, when they assemble the replicated HPV genomic DNA into infectious virions. L1 proteins are stable in two oligomeric configurations: as homopentameric capsomers, and as capsids composed of 72 capsomers. We found that intact L1 capsids of HPV type 11 cannot enter the nucleus, suggesting that capsid disassembly may be required for HPV11 L1 nuclear import. We established that HPV11 L1 is imported in a receptor-mediated manner into the nuclei of digitonin-permeabilized HeLa cells. HPV11 L1 docked at the nuclear pore complexes via karyopherin alpha2beta1 heterodimers. Anti-karyopherin-beta1 and anti-karyopherin alpha2 antibodies specifically inhibited nuclear import of HPV11 L1. Moreover, nuclear import of HPV11 L1 could be reconstituted using karyopherin alpha2, beta1, RanGDP and p10. In agreement with the docking and import data, we found that HPV11 L1 binds to karyopherin alpha2 and that this interaction is inhibited by a peptide representing the classical nuclear localization signal of SV40 T antigen. These results strongly suggest that HPV11 L1 enters the nucleus of the infected host cell via the karyopherin alpha2beta1 pathway.
人乳头瘤病毒（HPV）的L1主要衣壳蛋白在病毒生命周期的两个阶段进入宿主细胞核：1）感染后；2）在生产阶段后期，此时它们将复制的HPV基因组DNA组装成感染性病毒粒子。L1蛋白在两种寡聚体构型中是稳定的：作为同五聚体壳粒，以及作为由72个壳粒组成的衣壳。我们发现HPV11型的完整L1衣壳无法进入细胞核，这表明HPV11 L1核输入可能需要衣壳解体。我们证实HPV11 L1以受体介导的方式导入洋地黄皂苷通透的HeLa细胞核。HPV11 L1通过核转运蛋白α2β1异二聚体停靠在核孔复合体上。抗核转运蛋白-β1和抗核转运蛋白α2抗体特异性抑制HPV11 L1的核输入。此外，HPV11 L1的核输入可以使用核转运蛋白α2、β1、RanGDP和p10进行重建。与停靠和输入数据一致，我们发现HPV11 L1与核转运蛋白α2结合，并且这种相互作用被代表SV40 T抗原经典核定位信号的肽所抑制。这些结果强烈表明HPV11 L1通过核转运蛋白α2β1途径进入被感染宿主细胞的细胞核。
