PMC:4103454 / 2034-4439 JSONTXT

{"project":"2_test","denotations":[{"id":"24981866-20603016-20021720","span":{"begin":282,"end":286},"obj":"20603016"},{"id":"24981866-20671156-20021721","span":{"begin":300,"end":304},"obj":"20671156"},{"id":"24981866-20603015-20021722","span":{"begin":321,"end":325},"obj":"20603015"},{"id":"24981866-20603073-20021723","span":{"begin":348,"end":352},"obj":"20603073"},{"id":"24981866-23325218-20021724","span":{"begin":591,"end":595},"obj":"23325218"},{"id":"24981866-22772369-20021725","span":{"begin":770,"end":774},"obj":"22772369"},{"id":"24981866-24344280-20021726","span":{"begin":890,"end":894},"obj":"24344280"},{"id":"24981866-20603016-20021727","span":{"begin":1134,"end":1138},"obj":"20603016"},{"id":"24981866-20603015-20021728","span":{"begin":1155,"end":1159},"obj":"20603015"},{"id":"24981866-20603073-20021729","span":{"begin":1182,"end":1186},"obj":"20603073"},{"id":"24981866-16627993-20021730","span":{"begin":1527,"end":1531},"obj":"16627993"},{"id":"24981866-22638584-20021731","span":{"begin":1737,"end":1741},"obj":"22638584"},{"id":"24981866-15972856-20021732","span":{"begin":1875,"end":1879},"obj":"15972856"},{"id":"24981866-20603015-20021733","span":{"begin":2027,"end":2031},"obj":"20603015"}],"text":"Introduction\nFANCD2/FANCI-associated nuclease 1 (FAN1, hereafter hFAN1) is a structure-specific nuclease required for the repair of interstrand DNA crosslinks (ICL) and is recruited to sites of DNA damage in a manner dependent on the monoubiquitinated form of FANCD2 (Kratz et al., 2010, Liu et al., 2010, MacKay et al., 2010, Smogorzewska et al., 2010). Cells lacking FAN1 display increased sensitivity only to agents that induce ICLs. Mutations in humans in some of the genes involved in ICL repair cause Fanconi anemia, a rare chromosome instability disorder (Kottemann and Smogorzewska, 2013). Mutations in FAN1 have not been identified in FA patients but have been associated with karyomegalic interstitial nephritis, a form of chronic kidney disease (Zhou et al., 2012). In addition, FAN1 has been identified as a susceptibility gene for schizophrenia and autism (Ionita-Laza et al., 2014).\nhFAN1 has previously been shown to preferentially cleave branched DNA structures that mimic intermediates of DNA repair, with a strong preference in vitro for 5′ flap DNA. hFAN1 also possesses a 5′-3′ exonuclease activity (Kratz et al., 2010, MacKay et al., 2010, Smogorzewska et al., 2010). All FAN1 nuclease activities are mediated by a virus-type replication-repair nuclease (“VRR-Nuc”) domain located at the C terminus. This domain, which is conserved in all FAN1 orthologs, is a member of the ancient restriction endonuclease-like superfamily, with a predicted four-stranded mixed α/β fold with αβββαβ topology (Iyer et al., 2006). The active site of the members of this superfamily of enzymes has a conserved PDXn(D/E)XK motif, which in most cases is able to coordinate divalent metal ions required for activity (Steczkiewicz et al., 2012). VRR-Nuc domains were first identified through a combination of sequence homology and secondary structure prediction (Kinch et al., 2005). FAN1 is the only VRR-Nuc-domain-containing protein in eukaryotes, although there are many examples in bacteria and bacteriophage (MacKay et al., 2010), and in most of these cases, VRR-Nuc domains are present as single-domain proteins. Here, using a combination of structural and biochemical approaches allied to molecular modeling, we show how the oligomeric state of FAN1 orthologs and standalone VRR-Nuc domain proteins are directly related to their activities on asymmetric versus symmetric DNA substrates, respectively."}