Holzschu D L, Martineau D, Fodor S K, Vogt V M, Bowser P R, Casey J W
Department of Microbiology, Parasitology and Immunology, Cornell University, Ithaca, New York 14853, USA.
J Virol. 1995 Sep;69(9):5320-31. doi: 10.1128/JVI.69.9.5320-5331.1995.
Walleye dermal sarcoma virus (WDSV) is a fish retrovirus associated with the development of tumors in walleyes. We have determined the complete nucleotide sequence of a DNA clone of WDSV, the N-terminal amino acid sequences of the major proteins, and the start site for transcription. The long terminal repeat is 590 bp in length, with the U3 region containing consensus sequences likely to be involved in viral gene expression. A predicted histidyl-tRNA binding site is located 3 nucleotides distal to the 3' end of the long terminal repeat. Virus particles purified by isopycnic sedimentation followed by rate zonal sedimentation showed major polypeptides with molecular sizes of 90, 25, 20, 14, and 10 kDa. N-terminal sequencing of these allowed unambiguous assignment of the small polypeptides as products of the gag gene, including CA and NC, and the large polypeptide as the TM product of env. The 582-amino-acid (aa) Gag protein precursor is predicted to be myristylated as is found for most retroviruses. NC contains a single Cys-His motif like those found in all retroviruses except spumaviruses. The WDSV pro and pol genes are in the same translational reading frame as gag and thus apparently are translated after termination suppression. The env gene encodes a surface (SU) protein of 469 aa predicted to be highly glycosylated and a large transmembrane (TM) protein of 754 aa. The sequence of TM is unusual in that it ends in a very hydrophobic segment of 65 residues containing a single charged residue. Following the env gene are two nonoverlapping long open reading frames of 290 aa (orf-A) and 306 aa (orf-B), neither of which shows significant sequence similarity with known genes. A third open reading frame of 119 aa (orf-C) is located in the leader region preceding gag. The predicted amino acid sequence of reverse transcriptase would place WDSV phylogenetically closest to the murine leukemia virus-related genus of retroviruses. However, other members of this genus do not have accessory genes, suggesting that WDSV acquired orf-A, orf-B, and perhaps orf-C late in its evolution. We hypothesize by analogy with other complex retroviruses that the accessory genes of WDSV function in the regulation of transcription and in RNA processing and also in the induction of walleye dermal sarcoma.
大眼梭鲈皮肤肉瘤病毒（WDSV）是一种与大眼梭鲈肿瘤发生相关的鱼类逆转录病毒。我们已经确定了WDSV DNA克隆的完整核苷酸序列、主要蛋白质的N端氨基酸序列以及转录起始位点。长末端重复序列长度为590 bp，U3区域包含可能参与病毒基因表达的共有序列。一个预测的组氨酰 - tRNA结合位点位于长末端重复序列3'端下游3个核苷酸处。通过等密度沉降随后速率区带沉降纯化的病毒颗粒显示出分子量分别为90、25、20、14和10 kDa的主要多肽。对这些多肽进行N端测序后，明确将小多肽鉴定为gag基因的产物，包括CA和NC，而大多肽鉴定为env的TM产物。预测582个氨基酸（aa）的Gag蛋白前体如大多数逆转录病毒一样会被肉豆蔻酰化。NC含有一个单一的Cys - His基序，与除泡沫病毒外的所有逆转录病毒中的基序相似。WDSV的pro和pol基因与gag处于相同的翻译阅读框，因此显然是在终止抑制后翻译的。env基因编码一个预测为高度糖基化的469 aa表面（SU）蛋白和一个754 aa的大跨膜（TM）蛋白。TM的序列不同寻常，因为它在一个由65个残基组成的非常疏水的片段末端结束，该片段包含一个带电荷的残基。在env基因之后是两个不重叠的长开放阅读框，分别为290 aa（orf - A）和306 aa（orf - B），它们与已知基因均无显著序列相似性。一个119 aa的第三个开放阅读框（orf - C）位于gag之前的前导区域。逆转录酶的预测氨基酸序列表明WDSV在系统发育上与逆转录病毒中与鼠白血病病毒相关的属最为接近。然而，该属的其他成员没有辅助基因，这表明WDSV在其进化后期获得了orf - A、orf - B，可能还有orf - C。我们通过与其他复杂逆转录病毒类比推测，WDSV的辅助基因在转录调控、RNA加工以及大眼梭鲈皮肤肉瘤的诱导中发挥作用。
