Ishii Yoshiyuki, Ozaki Saori, Tanaka Keiko, Kanda Tadahito
Division of Molecular Genetics, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, 162-8640, Tokyo, Japan.
Virus Genes. 2005 Dec;31(3):321-8. doi: 10.1007/s11262-005-3250-3.
The human papillomavirus (HPV) capsomeres (pentamers of major capsid protein L1), which constitute along with L2 the virion capsid, can assemble themselves alone into the L1-capsid particles in vivo and in vitro, depending on intercapsomeric disulfide bonds. To study a possible role of L2 in capsid assembly, we examined the interaction between HPV16 L2 and capsomeres under the conditions that inhibit the formation of disulfide bonds in vitro and in vivo. The purified L2 bound to free capsomeres prepared by disassembling L1-capsids but not to the L1-capsids in vitro. And the L2 was found to help capsomeres assemble into smaller capsid-like particles independently of intercapsomeric disulfide bonding. Similar particles were obtained from the Sf9 cells co-infected with baculoviruses expressing L2 and an L1 mutant that lacks a C-terminal cysteine (C428S) and can form capsomeres but no capsids when expressed alone. These findings suggest that L2, which is known to bind both viral DNA and L1, may contribute to the formation of the virion by linking viral DNA and capsomeres and by helping capsomeres assemble before the virion capsid structure is completed by dintercapsomeric disulfide bonding.
人乳头瘤病毒（HPV）的衣壳粒（主要衣壳蛋白L1的五聚体）与L2共同构成病毒粒子衣壳，其可在体内和体外单独组装成L1衣壳颗粒，这依赖于衣壳粒间的二硫键。为了研究L2在衣壳组装中可能发挥的作用，我们在体外和体内抑制二硫键形成的条件下，检测了HPV16 L2与衣壳粒之间的相互作用。纯化后的L2在体外可与通过拆解L1衣壳制备的游离衣壳粒结合，但不能与L1衣壳结合。并且发现L2可帮助衣壳粒独立组装成较小的衣壳样颗粒，而不依赖于衣壳粒间的二硫键连接。从共感染了表达L2的杆状病毒和一种L1突变体（缺少C端半胱氨酸，即C428S，单独表达时可形成衣壳粒但不能形成衣壳）的Sf9细胞中也获得了类似颗粒。这些发现表明，已知可同时结合病毒DNA和L1的L2，可能通过连接病毒DNA和衣壳粒，以及在衣壳粒间二硫键连接完成病毒粒子衣壳结构之前帮助衣壳粒组装，从而有助于病毒粒子的形成。
