Garber E A, Hreniuk D L, Scheidel L M, van der Ploeg L H
Department of Genetics and Molecular Biology, Merck Research Laboratories, Rahway, New Jersey 07065.
Virology. 1993 Jun;194(2):715-23. doi: 10.1006/viro.1993.1312.
Murine Mx1 is a nuclear localized protein of 631 amino acids with antiviral activity against influenza virus. Fourteen mutations in murine Mx1 were constructed in vitro, expressed in chicken embryo fibroblasts via replication-competent retroviruses, and the effects of the mutations on Mx localization and antiviral activity were assayed. The results suggest that a nuclear location is not sufficient for antiviral activity, that there are intricate structural constrains on the Mx protein for antiviral activity and that multiple domains of the Mx protein are required for the characteristic punctate nuclear Mx distribution. These conclusions are based on the findings showing that: (i) none of the mutants retained antiviral activity; (ii) only a mutant with a Leu to Lys substitution at residue 612 within the nuclear targeting signal retained the characteristic punctate nuclear localization of wildtype Mx1; (iii) diffuse nuclear localization was observed for mutants with substitutions of Pro for Leu at residue 619, 626, or both 619 and 626, and deletions of residues 23 to 95, 159 to 185, 369 to 409, 387 to 440, 522 to 560, or 541 to 596; and (iv) cytoplasmic localization was observed for mutants with carboxy-terminal truncations of 15, 30, or 61 amino acids, or a deletion of residues 610 to 624.
小鼠Mx1是一种由631个氨基酸组成的核定位蛋白，具有抗流感病毒的活性。在体外构建了小鼠Mx1的14个突变体，通过具有复制能力的逆转录病毒在鸡胚成纤维细胞中表达，并检测了这些突变对Mx定位和抗病毒活性的影响。结果表明，核定位不足以产生抗病毒活性，Mx蛋白的抗病毒活性存在复杂的结构限制，并且Mx蛋白的多个结构域对于其特征性的点状核内分布是必需的。这些结论基于以下发现：(i) 所有突变体均未保留抗病毒活性；(ii) 仅在核定位信号内第612位残基处由亮氨酸替换为赖氨酸的突变体保留了野生型Mx1特征性的点状核定位；(iii) 在第619、626位残基或619和626位残基处由脯氨酸替换亮氨酸的突变体，以及缺失第23至95、159至185、369至409、387至440、522至560或541至596位残基的突变体，观察到弥散性核定位；(iv) 在羧基末端截短15个、30个或61个氨基酸，或缺失第610至624位残基的突变体中观察到细胞质定位。
