你是否有質(zhì)疑過為什么遺傳了媽媽的笑容而不是爸爸的身高,？來自英國利茲大學(xué)（The University of Leeds）分子與細(xì)胞生物學(xué)研究所,，鄧迪大學(xué)（University of Dundee）的研究人員為解開這一疑惑：自然如何將母本和父本DNA融合起來創(chuàng)造出獨(dú)一無二的下一代？Simon Phillips教授,、Stephen Carr和Jonathan Hadden博士在世界上首次獲得了一種DNA雙鏈裂解的關(guān)鍵酶的3維結(jié)構(gòu),。這一研究成果公布在《自然》雜志上。
T7內(nèi)切酶I結(jié)構(gòu)的發(fā)現(xiàn)是通過X射線結(jié)晶學(xué)技術(shù)完成的,，這種酶從一種噬菌體——這種噬菌體與病毒相似,，能攻擊細(xì)菌，但是其分子過程與其它生物體,，比如人類的相似,。
Phillips教授表示，“雖然大家都了解這種酶起著重要的作用,，但是其物理結(jié)構(gòu)——對于深度剖析作用過程至關(guān)重要,，至今并沒有觀測到過，現(xiàn)在我們獲得了這一酶的3D結(jié)構(gòu),，并且觀測到了其切斷DNA鏈的那個(gè)作用點(diǎn),，這對于了解DNA工作的基礎(chǔ)機(jī)制，以及病毒如何復(fù)制體內(nèi)DNA來說是一個(gè)重要的突破,。”
人類中,，這個(gè)過程開始于父本和母本的DNA鏈在任意序列融合的時(shí)候，像是T7內(nèi)切酶I這樣的酶在這個(gè)交聯(lián)過程中起著重要的作用,，創(chuàng)造出后代獨(dú)一無二的第三種序列,。
但是Phillips教授也表示在這個(gè)過程之前有時(shí)也可以觀測到交聯(lián)，“這是一個(gè)十分重要的過程，我們下一步希望能在比噬菌體更加復(fù)雜的體系,，比如酵母中檢測這一過程,。”
原始出處:
Nature 449, 621-624 (4 October 2007) | doi:10.1038/nature06158; Received 24 May 2007; Accepted 7 August 2007; Published online 16 September 2007
The structural basis of Holliday junction resolution by T7 endonuclease I
Jonathan M. Hadden1, Anne-Cécile Déclais2, Stephen B. Carr1, David M. J. Lilley2 & Simon E. V. Phillips1
Astbury Centre for Structural Molecular Biology, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
Cancer Research UK Nucleic Acid Structure Research Group, MSI/WTB complex, University of Dundee, Dundee DD1 4HN, UK
Correspondence to: Simon E. V. Phillips1 Correspondence and requests for materials should be addressed to S.E.V.P. (Email: [email protected]).
The four-way (Holliday) DNA junction is the central intermediate in homologous recombination, a ubiquitous process that is important in DNA repair and generation of genetic diversity1. The penultimate stage of recombination requires resolution of the DNA junction into nicked-duplex species by the action of a junction-resolving enzyme, examples of which have been identified in a wide variety of organisms2. These enzymes are nucleases that are highly selective for the structure of branched DNA. The mechanism of this selectivity has, however, been unclear in the absence of structural data. Here we present the crystal structure of the junction-resolving enzyme phage T7 endonuclease I in complex with a synthetic four-way DNA junction. Although the enzyme is structure-selective, significant induced fit occurs in the interaction, with changes in the structure of both the protein and the junction. The dimeric enzyme presents two binding channels that contact the backbones of the junction's helical arms over seven nucleotides. These interactions effectively measure the relative orientations and positions of the arms of the junction, thereby ensuring that binding is selective for branched DNA that can achieve this geometry.
