From the Fels Institute for Cancer Research, Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, Pennsylvania, 19140.
From the Fels Institute for Cancer Research, Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, Pennsylvania, 19140
J Biol Chem. 2018 Apr 6;293(14):5259-5269. doi: 10.1074/jbc.RA117.000565. Epub 2018 Feb 14.
is a unique multifunctional replication and repair gene that encodes for a N-terminal superfamily 2 helicase and a C-terminal A-family polymerase. Although the function of the polymerase domain has been investigated, little is understood regarding the helicase domain. Multiple studies have reported that polymerase θ-helicase (Polθ-helicase) is unable to unwind DNA. However, it exhibits ATPase activity that is stimulated by single-stranded DNA, which presents a biochemical conundrum. In contrast to previous reports, we demonstrate that Polθ-helicase (residues 1-894) efficiently unwinds DNA with 3'-5' polarity, including DNA with 3' or 5' overhangs, blunt-ended DNA, and replication forks. Polθ-helicase also efficiently unwinds RNA-DNA hybrids and exhibits a preference for unwinding the lagging strand at replication forks, similar to related HELQ helicase. Finally, we find that Polθ-helicase can facilitate strand displacement synthesis by Polθ-polymerase, suggesting a plausible function for the helicase domain. Taken together, these findings indicate nucleic acid unwinding as a relevant activity for Polθ in replication repair.
是一个独特的多功能复制和修复基因，编码一个 N 端超家族 2 解旋酶和一个 C 端 A 家族聚合酶。虽然聚合酶结构域的功能已经被研究过，但对于解旋酶结构域的了解甚少。多项研究报告称，聚合酶θ解旋酶（Polθ-helicase）无法解开 DNA。然而，它表现出 ATP 酶活性，这种活性被单链 DNA 所刺激，这提出了一个生化难题。与之前的报告相反，我们证明 Polθ-helicase（残基 1-894）能够有效地以 3'-5'极性解开 DNA，包括具有 3'或 5'突出端、平端 DNA 和复制叉的 DNA。Polθ-helicase 还能有效地解开 RNA-DNA 杂交体，并表现出在复制叉处优先解开滞后链的偏好，类似于相关的 HELQ 解旋酶。最后，我们发现 Polθ-helicase 可以促进 Polθ-聚合酶的链置换合成，这表明解旋酶结构域具有合理的功能。总之，这些发现表明核酸解旋是 Polθ 在复制修复中的一个相关活性。
