Protein dynamics on the lagging strand during DNA synthesis

DNA replication is one of the vital processes in the cell; it duplicates chromosomal DNA before a cell divides. In all organisms, DNA synthesis on the leading-strand template occurs continuously, whereas on the lagging strand a different mechanism is required. Due to the anti-parallel structure of double-stranded DNA, lagging-strand synthesis requires repeated RNA priming by a specialist primase and synthesis of short Okazaki fragments. How proteins carry out this dynamic process is still unknown. For Escherichia coli DNA replication, a lagging-strand three-point switch was proposed in 1999 to explain priming by DnaG primase while it is associated with the DnaB6 helicase, and its subsequent hand-off from the primer to the χ subunit of DNA polymerase III holenzyme to enable primer utilization for Okazaki fragment synthesis. The main aims of this project were to study the interactions involved in this switch to understand better how the proteins coordinate their roles during lagging-strand DNA synthesis.