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E. coli DNA replication in the absence of free β clamps
Author(s) -
Tanner Nathan A,
Tolun Gökhan,
Loparo Joseph J,
Jergic Slobodan,
Griffith Jack D,
Dixon Nicholas E,
van Oijen Antoine M
Publication year - 2011
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2011.84
Subject(s) - okazaki fragments , replisome , biology , dnag , dna replication , primase , prokaryotic dna replication , dna clamp , dna polymerase , primer (cosmetics) , microbiology and biotechnology , dna , biophysics , genetics , eukaryotic dna replication , rna , gene , chemistry , reverse transcriptase , organic chemistry
During DNA replication, repetitive synthesis of discrete Okazaki fragments requires mechanisms that guarantee DNA polymerase, clamp, and primase proteins are present for every cycle. In Escherichia coli , this process proceeds through transfer of the lagging‐strand polymerase from the β sliding clamp left at a completed Okazaki fragment to a clamp assembled on a new RNA primer. These lagging‐strand clamps are thought to be bound by the replisome from solution and loaded a new for every fragment. Here, we discuss a surprising, alternative lagging‐strand synthesis mechanism: efficient replication in the absence of any clamps other than those assembled with the replisome. Using single‐molecule experiments, we show that replication complexes pre‐assembled on DNA support synthesis of multiple Okazaki fragments in the absence of excess β clamps. The processivity of these replisomes, but not the number of synthesized Okazaki fragments, is dependent on the frequency of RNA‐primer synthesis. These results broaden our understanding of lagging‐strand synthesis and emphasize the stability of the replisome to continue synthesis without new clamps.