Publication Date:
2019
Description:
〈p〉The replisome that performs concerted leading and lagging DNA strand synthesis at a replication fork has never been visualized in atomic detail. Using bacteriophage T7 as a model system, we determined cryo-EM structures up to 3.2 Å of helicase translocating along DNA, and of helicase-polymerase-primase complexes engaging in synthesis of both DNA strands. Each domain of the spiral-shaped hexameric helicase translocates hand-over-hand sequentially along a ssDNA coil, akin to the way AAA+ ATPases unfold peptides. Two lagging-strand polymerases are attached to the primase ready for Okazaki-fragment synthesis in tandem. A β-hairpin from the leading-strand polymerase separates two parental DNA strands into a T-shaped fork, thus enabling the closely coupled helicase to advance perpendicular to the downstream DNA duplex. These structures reveal the molecular organization and operating principles of a replisome.〈/p〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Natural Sciences in General
