Wang A L, Yang H M, Shen K A, Wang C C
Department of Pharmaceutical Chemistry, University of California, San Francisco 94143-0446.
Proc Natl Acad Sci U S A. 1993 Sep 15;90(18):8595-9. doi: 10.1073/pnas.90.18.8595.
Giardiavirus is a small, nonenveloped virus comprising a monopartite double-stranded RNA genome, a major protein of 100 kDa, and a less abundant polypeptide of 190 kDa. It can be isolated from the culture supernatant of Giardia lamblia, a parasitic flagellate in human and other mammals, and efficiently infects other virus-free G. lamblia. A single-stranded copy of the viral RNA can be electroporated into uninfected G. lamblia cells to complete the viral replication cycle. Giardiavirus genomic cDNA of 6100 nt was constructed and its sequence revealed the presence of two large open reading frames that are separated by a -1 frameshift and share an overlap of 220 nt. The 3' open reading frame contains all consensus RNA-dependent RNA polymerase sequence motifs. A heptamer-pseudoknot structure similar to those found at ribosomal slippage sites in retroviruses and yeast killer virus was identified within this overlap. Immunostudies using antisera against synthesized peptides from four regions in the two open reading frames indicated that the 100- and 190-kDa viral proteins share a common domain in the amino-terminal region. But the 190-kDa protein makes a -1 switch of its reading frame beyond the presumed slippage heptamer and is therefore a -1 frameshift fusion protein similar to the gag-pol fusion protein found in retroviruses.
贾第虫病毒是一种小型无包膜病毒，其基因组由单片段双链RNA组成，有一个100 kDa的主要蛋白和一个含量较少的190 kDa多肽。它可从人及其他哺乳动物体内的寄生鞭毛虫——蓝氏贾第鞭毛虫的培养上清液中分离得到，并能有效感染其他无病毒的蓝氏贾第鞭毛虫。病毒RNA的单链拷贝可通过电穿孔导入未感染的蓝氏贾第鞭毛虫细胞，以完成病毒复制周期。构建了6100 nt的贾第虫病毒基因组cDNA，其序列显示存在两个大的开放阅读框，它们由一个 -1移码隔开，且有220 nt的重叠区域。3' 开放阅读框包含所有保守的依赖RNA的RNA聚合酶序列基序。在该重叠区域内鉴定出一种七聚体假结结构，类似于在逆转录病毒和酵母杀伤病毒的核糖体滑动位点发现的结构。使用针对两个开放阅读框中四个区域合成肽的抗血清进行的免疫研究表明，100 kDa和190 kDa的病毒蛋白在氨基末端区域有一个共同结构域。但190 kDa的蛋白在假定的滑动七聚体之后发生 -1 读框转换，因此是一种 -1 移码融合蛋白，类似于在逆转录病毒中发现的gag-pol融合蛋白。
