POLN, a nuclear PolA family DNA polymerase homologous to the DNA cross-link sensitivity protein Mus308
POLN, a nuclear PolA family DNA polymerase homologous to the DNA cross-link sensitivity protein Mus308
复制标题
DOI：
10.1074/jbc.m305646200
复制
发表时间：
2003-08-22
影响因子：
4.8
通讯作者：
Wood, RD
中科院分区：
文献类型：
--
作者：
Marini, F;Kim, N;Wood, RD
果蝇 Mus308 基因在编码 A 家族 DNA 聚合酶结构域和 DNA/RNA 解旋酶结构域方面很不寻常。 mus308 突变被证明会导致对 DNA 交联剂的敏感性增加，从而得出 Mus308 在 DNA 链间交联修复中发挥作用的假设。最近，Mus308 的哺乳动物直系同源物 POLQ 已被鉴定。我们在此报告 POLN 及其基因产物（一种也与 Mus308 相关的新哺乳动物 DNA 聚合酶）的鉴定、克隆和表征。人类 cDNA 编码 900 个氨基酸残基的蛋白质。从残基 419 开始的区域与大肠杆菌 DNA 聚合酶 I 的等效区域有 33% 的同一性（48% 相似性）。 POLN 在人类细胞系中表达，具有大量可变剪接转录物，以及包含 160 kilobase 基因组 DNA 内的 24 个外显子的全长人类编码区。通过 Northern 印迹和原位杂交进行的表达分析表明，全长 POLN 在人和小鼠睾丸中表达最高。当 POLN 在人成纤维细胞中表达为增强型绿色荧光蛋白 (GFP) 标记蛋白时，定位于细胞核。 GFP 标记的重组 POLN 对活化的小牛胸腺 DNA 和单引物模板具有 DNA 聚合酶活性。
The Drosophila Mus308 gene is unusual in encoding both a family A DNA polymerase domain and a DNA/RNA helicase domain. A mus308 mutation was shown to result in increased sensitivity to DNA cross-linking agents, leading to the hypothesis that Mus308 functions in the repair of DNA interstrand cross-links. Recently a mammalian ortholog of Mus308, POLQ, has been identified. We report here the identification, cloning, and characterization of POLN and its gene product, a new mammalian DNA polymerase also related to Mus308. The human cDNA encodes a protein of 900 amino acid residues. The region starting from residue 419 shares 33% identity (48% similarity) with the equivalent region of Escherichia coli DNA polymerase I. POLN is expressed in human cell lines with numerous alternatively spliced transcripts, and a full-length human coding region that comprises 24 exons within 160 kilobases of genomic DNA. Expression analysis by northern blotting and in situ hybridization showed highest expression of full-length POLN in human and mouse testis. POLN localized to the nucleus when expressed as a enhanced green fluorescent protein (GFP)-tagged protein in human fibroblasts. GFP-tagged recombinant POLN had DNA polymerase activity on activated calf thymus DNA and on a singly primed template.