Human KIAA1018/FAN1 localizes to stalled replication forks via its ubiquitin-binding domain.

Genome maintenance pathways correct aberrations in DNA that would be deleterious to the organism. A crucial element of many genome maintenance processes is the ability to degrade DNA that either contains errors or obscures useful substrates for recombination and/or repair by means of nucleases. We have examined a putative nuclease that has heretofore been unreported, KIAA1018/FAN1.

Identification of the SSB binding site on E. coli RecQ reveals a conserved surface for binding SSB's C terminus.

RecQ DNA helicases act in conjunction with heterologous partner proteins to catalyze DNA metabolic activities, including recombination initiation and stalled replication fork processing. For the prototypical Escherichia coli RecQ protein, direct interaction with single-stranded DNA-binding protein (SSB) stimulates its DNA unwinding activity. Complex formation between RecQ and SSB is mediated by the RecQ winged-helix domain, which binds the nine C-terminal-most residues of SSB, a highly conserved sequence known as the SSB-Ct element.

SSB as an organizer/mobilizer of genome maintenance complexes.

When duplex DNA is altered in almost any way (replicated, recombined, or repaired), single strands of DNA are usually intermediates, and single-stranded DNA binding (SSB) proteins are present. These proteins have often been described as inert, protective DNA coatings. Continuing research is demonstrating a far more complex role of SSB that includes the organization and/or mobilization of all aspects of DNA metabolism.

A central role for SSB in Escherichia coli RecQ DNA helicase function.

RecQ DNA helicases are critical components of DNA replication, recombination, and repair machinery in all eukaryotes and bacteria. Eukaryotic RecQ helicases are known to associate with numerous genome maintenance proteins that modulate their cellular functions, but there is little information regarding protein complexes involving the prototypical bacterial RecQ proteins. Here we use an affinity purification scheme to identify three heterologous proteins that associate with Escherichia coli RecQ: SSB (single-stranded DNA-binding protein), exonuclease I, and RecJ exonuclease.