科學(xué)家已經(jīng)利用單分子分析研究了DNA復(fù)制的基本細(xì)胞過(guò)程,，這可能為DNA復(fù)制的機(jī)制提供見解，并闡明這類高分辨率研究的效用,。
在DNA復(fù)制期間,，一大群蛋白質(zhì)和酶讓雙螺旋解旋，并合成出與父鏈互補(bǔ)的新的DNA鏈,。DNA合成是被一個(gè)叉形的連續(xù)動(dòng)作引導(dǎo)的,，兩個(gè)分支——分別稱為先導(dǎo)鏈和后隨鏈——加入到了螺旋結(jié)構(gòu)中。這種蛋白質(zhì)群稱為復(fù)制體,，它與DNA聚合酶連在一起,，后者把核苷加到先導(dǎo)鏈和后隨鏈上，這兩個(gè)鏈?zhǔn)峭瑫r(shí)合成的,。
在實(shí)時(shí)實(shí)驗(yàn)中,，Mike O’Donnell及其同事分析了大腸桿菌復(fù)制體在DNA復(fù)制期間的運(yùn)動(dòng)，這讓他們可以既研究DNA復(fù)制率,，又研究聚合酶的連續(xù)性（連續(xù)性衡量的是這種酶離開DNA之前把多少核苷加到了正在復(fù)制的鏈上）,。這組作者說(shuō)，盡管后隨鏈合成顯著增加了復(fù)制體的連續(xù)性,，它減少了復(fù)制叉過(guò)程的總體復(fù)制率,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS August 3, 2009, doi: 10.1073/pnas.0906157106
Single-molecule analysis reveals that the lagging strand increases replisome processivity but slows replication fork progression
Nina Y. Yao,1, Roxana E. Georgescu,1, Jeff Finkelstein and Michael E. O'Donnell,2
1 Howard Hughes Medical Institute, Rockefeller University, 1230 York Avenue, New York, NY 10021
Single-molecule techniques are developed to examine mechanistic features of individual E. coli replisomes during synthesis of long DNA molecules. We find that single replisomes exhibit constant rates of fork movement, but the rates of different replisomes vary over a surprisingly wide range. Interestingly, lagging strand synthesis decreases the rate of the leading strand, suggesting that lagging strand operations exert a drag on replication fork progression. The opposite is true for processivity. The lagging strand significantly increases the processivity of the replisome, possibly reflecting the increased grip to DNA provided by 2 DNA polymerases anchored to sliding clamps on both the leading and lagging strands.
