Choi Eun-Young, Newman Ann E, Burger Lisa, Pintel David
Department of Molecular Microbiology and Immunology, Life Sciences Center, School of Medicine, University of Missouri-Columbia, 65211-7310, USA.
J Virol. 2005 Oct;79(19):12375-81. doi: 10.1128/JVI.79.19.12375-12381.2005.
Following transfection of murine fibroblasts, the lymphotropic strain of minute virus of mice (MVMi) does not efficiently produce progeny single-strand DNA (ssDNA). However, changing a single nucleotide in the MVMi 3' splice site to that found in the fibrotropic strain MVMp enabled full DNA replication and production of ssDNA. This change enhanced excision of the large intron and the production of NS2, likely by improving interaction, in fibroblasts with the branch point-binding U2 snRNA. One function of NS2 involves interaction with the nuclear export protein Crm1. The defect in production of MVMi ssDNA in fibroblasts can also be overcome by introducing a mutation in MVMi NS2 that enhances its interaction with Crm1. Although MVMi contains a 3' splice site that performs poorly in fibroblasts, MVMi generated at least as much R2 and NS2 in murine lymphocytes as did MVMp in fibroblasts. Therefore, it appears that MVMp has acquired a mutation that improves the excision of the large intron, as it adapted to fibroblasts to accommodate the need for NS2 for replication in these cells, and that the ratio of NS1 to NS2 may play a larger role in the host range of MVM than previously appreciated.
在对小鼠成纤维细胞进行转染后，小鼠微小病毒的嗜淋巴细胞株（MVMi）不能有效地产生子代单链DNA（ssDNA）。然而，将MVMi 3'剪接位点的一个单核苷酸改变为亲纤维性毒株MVMp中的相应核苷酸，可实现完全的DNA复制并产生ssDNA。这种改变增强了大内含子的切除以及NS2的产生，这可能是通过改善成纤维细胞中与分支点结合的U2 snRNA的相互作用来实现的。NS2的一个功能涉及与核输出蛋白Crm1的相互作用。在成纤维细胞中，通过在MVMi NS2中引入一个增强其与Crm1相互作用的突变，也可以克服MVMi ssDNA产生的缺陷。尽管MVMi含有一个在成纤维细胞中功能不佳的3'剪接位点，但MVMi在小鼠淋巴细胞中产生的R2和NS2至少与MVMp在成纤维细胞中产生的一样多。因此，似乎MVMp在适应成纤维细胞以满足在这些细胞中复制对NS2的需求时，获得了一个改善大内含子切除的突变，并且NS1与NS2的比例可能在MVM的宿主范围中发挥比之前所认识到的更大的作用。
