Harris J M, Haynes R H, McIntosh E M
Department of Biochemistry, University of Queensland, St. Lucia, Australia.
Biochem Cell Biol. 1997;75(2):143-51.
Amino acid sequence comparisons have revealed that a potential dUTPase gene is encoded by the retrovirus HERV-K, a defective multicopy virus that is transmitted vertically in humans. This gene is distinct from the human cellular dUTPase gene and thus two potential sources of the enzyme exist in human cells. dUTPases characterized from various sources each contain five conserved amino acid sequence motifs that form the active site of the enzyme. The protein sequence of the putative HERV-K dUTPase deduced from previous DNA sequence data from one proviral clone (HERV-K10) shows marked deviations at highly conserved residues in four of five of these motifs. Therefore, the reported DNA sequence may represent a mutated form of the viral dUTPase gene. To address this possibility, we cloned and sequenced 22 copies of the HERV-K dUTPase gene from human DNA. The results of this analysis indicate that variations evident in the HERV-K10 dUTPase amino acid sequence represent mutations of the wild-type viral DNA sequence. A version of the HERV-K dUTPase gene that corresponds to the ancestral, wild-type DNA sequence was constructed and adapted for expression in Escherichia coli. The resulting enzyme was found to exhibit properties similar to those of dUTPases isolated from other systems. A possible role of the HERV-K dUTPase in human disease is discussed.
氨基酸序列比较显示，逆转录病毒HERV-K编码了一个潜在的dUTPase基因，HERV-K是一种有缺陷的多拷贝病毒，可在人类中垂直传播。该基因与人类细胞dUTPase基因不同，因此人类细胞中存在该酶的两个潜在来源。从各种来源鉴定的dUTPase均包含五个保守的氨基酸序列基序，这些基序构成了该酶的活性位点。根据先前来自一个前病毒克隆（HERV-K10）的DNA序列数据推导的假定HERV-K dUTPase的蛋白质序列在这五个基序中的四个基序的高度保守残基处显示出明显偏差。因此，报道的DNA序列可能代表病毒dUTPase基因的突变形式。为了探究这种可能性，我们从人类DNA中克隆并测序了22个HERV-K dUTPase基因拷贝。该分析结果表明，HERV-K10 dUTPase氨基酸序列中明显的变异代表野生型病毒DNA序列的突变。构建了与原始野生型DNA序列相对应的HERV-K dUTPase基因版本，并使其适合在大肠杆菌中表达。发现所得的酶表现出与从其他系统分离的dUTPase相似的特性。讨论了HERV-K dUTPase在人类疾病中的可能作用。
