Sahli R, Freund R, Dubensky T, Garcea R, Bronson R, Benjamin T
Department of Pathology, Harvard Medical School, Boston, MA 02115.
Virology. 1993 Jan;192(1):142-53. doi: 10.1006/viro.1993.1016.
We have examined effects of mutations of the minor capsid proteins VP2 and VP3 of polyoma virus. Infection of cells by mutants blocked in expression of either VP2 or VP3 by alterations of their initiator methionine codons led to the rapid selection of wild-type revertants. This reversion suggests a strong, if not absolute, requirement for both proteins in virus growth. A mutant virus, VP2*, in which alanine was substituted for glycine-2, expressed a nonmyristylated form of VP2 that was incorporated into virions. Studies of VP2* revealed a 15- to 20-fold lower specific infectivity and a delay in growth in both primary and established mouse cells compared to wild-type virus. Analysis of the growth delay indicated a defect in an early step of infection, at or prior to uncoating. Synthesis of viral DNA and VP1 was delayed by about 9 hr in mutant compared to that in wild-type infected cells. No evidence was obtained for an effect on either virus assembly (encapsidation) or stability of virions. Infection of mice by the VP2* mutant virus resulted in attenuated virus replication and tumor induction which were much more severely affected following intranasal inoculation than intraperitoneal inoculation.
我们研究了多瘤病毒小衣壳蛋白VP2和VP3突变的影响。通过改变起始甲硫氨酸密码子而阻断VP2或VP3表达的突变体感染细胞后，会迅速选择出野生型回复体。这种回复表明病毒生长对这两种蛋白有强烈（即使不是绝对）的需求。一种突变病毒VP2*，其中丙氨酸取代了甘氨酸-2，表达出一种未豆蔻酰化的VP2形式，该形式被整合到病毒粒子中。对VP2的研究表明，与野生型病毒相比，其在原代和已建立的小鼠细胞中的比感染性低15至20倍，且生长延迟。对生长延迟的分析表明，在感染的早期步骤（脱壳时或脱壳前）存在缺陷。与野生型感染细胞相比，突变体中病毒DNA和VP1的合成延迟约9小时。未获得对病毒装配（衣壳化）或病毒粒子稳定性有影响的证据。VP2突变病毒感染小鼠导致病毒复制和肿瘤诱导减弱，鼻内接种后比腹腔接种受影响更严重。
