Driving past four-stranded snags

摘要

Genomic DNA is long, shows profound sequence redundancy and is heavily tangled. These properties create formidable problems during DNA replication — the process at the heart of heredity. A particular obstacle is the presence of repetitive runs of DNA that can form unusual structures such as hairpins, cruciforms, three-stranded triplexes and four-stranded G-quadruplexes. In this issue, Paeschke et al.~1(page 458) describe an evolutionary conserved mechanism that promotes replication past G-quadruplexes.%Pif1家族的DNA解旋酶从细菌到人类都是高度rn保守的。Virginia Zakian及其同事发现，在酵母rn中，人PIF1能够展开一个被称为G-quadruplexrn的四链结构。在此过程中，它抑制在这样的结rn构上出现的基因组不稳定性。人类的这种蛋白rn能够在酵母中提供补充的能力，显示了这种活rn性在整个演化过程中的重要性。