State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Rd., Jinan 250100, People's Republic of China.
Extremophiles. 2011 Jan;15(1):67-76. doi: 10.1007/s00792-010-0338-z. Epub 2010 Dec 5.
XPB helicase is the largest subunit of transcription factor IIH (TFIIH), a ten-subunit protein complex essential for transcription initiation and nucleotide excision repair (NER) in Eukarya. Two XPB homologues (XPBI and XPBII) are present in the genome of most crenarchaeota, one of the two major phyla of archaea; however, the biochemical properties have not been fully characterized and their cellular roles have not been clearly defined. Here, we report that XPBI from the hyperthermophilic crenarchaeon Sulfolobus tokodaii (StoXPBI) is able to destabilize double-stranded DNA (dsDNA) helix independent of ATP (designated as dsDNA melting activity). This activity is inhibited by single-stranded DNA (ssDNA) and relies on the unique N-terminal domain of StoXPBI, which is also likely responsible for the intrinsic strong ssDNA binding activity of StoXPBI as revealed by deletion analysis. We demonstrate that the ATPase activity of StoXPBII is remarkably stimulated by StoBax1, a nuclease partner of StoXPBII. The role of the unique dsDNA melting activity of XPBI in NER in archaea was discussed.
XPB 解旋酶是转录因子 IIH（TFIIH）的最大亚基，TFIIH 是一种由十个亚基组成的蛋白质复合物，对于真核生物的转录起始和核苷酸切除修复（NER）至关重要。大多数古菌的基因组中都存在两个 XPB 同源物（XPB1 和 XPB2），古菌是两个主要的古菌门之一；然而，其生化特性尚未完全表征，其细胞功能也尚未明确界定。在这里，我们报告说，来自嗜热古菌 Sulfolobus tokodaii（StoXPB1）的 XPB1 能够在不依赖 ATP 的情况下破坏双链 DNA（dsDNA）螺旋（称为 dsDNA 解链活性）。该活性被单链 DNA（ssDNA）抑制，并依赖于 StoXPB1 的独特 N 端结构域，该结构域也可能负责 StoXPB1 的固有强 ssDNA 结合活性，这是通过缺失分析揭示的。我们证明了 StoBax1 可显著刺激 StoXPB2 的 ATP 酶活性，StoBax1 是 StoXPB2 的核酸酶伴侣。还讨论了 XPB1 在古菌 NER 中的独特 dsDNA 解链活性的作用。
