Author response: Cryo-EM structures reveal that RFC recognizes both the 3′- and 5′-DNA ends to load PCNA onto gaps for DNA repair
Year: 2022
Type: peer-review
Abstract: Article Figures and data Abstract Editor's evaluation Introduction Results Discussion Materials and methods Data availability References Decision letter Author response Article and author information Metrics Abstract RFC uses ATP to assemble PCNA onto primed sites for replicative DNA polymerases δ and ε. The RFC pentamer forms a central chamber that binds 3′ ss/ds DNA junctions to load PCNA onto DNA during replication. We show here five structures that identify a second DNA binding site in RFC that binds a 5′ duplex. This 5′ DNA site is located between the N-terminal BRCT domain and AAA+ module of the large Rfc1 subunit. Our structures reveal ideal binding to a 7-nt gap, which includes 2 bp unwound by the clamp loader. Biochemical studies show enhanced binding to 5 and 10 nt gaps, consistent with the structural results. Because both 3′ and 5′ ends are present at a ssDNA gap, we propose that the 5′ site facilitates RFC’s PCNA loading activity at a DNA damage-induced gap to recruit gap-filling polymerases. These findings are consistent with genetic studies showing that base excision repair of gaps greater than 1 base requires PCNA and involves the 5′ DNA binding domain of Rfc1. We further observe that a 5′ end facilitates PCNA loading at an RPA coated 30-nt gap, suggesting a potential role of the RFC 5′-DNA site in lagging strand DNA synthesis. Editor's evaluation The role of Replication Factor C (RFC) in DNA replication and repair has been known for many years. RFC/PCNA binds to a double strand-single strand DNA junction with a 3'-recessed end, with the DNA passing through a central chamber in the five-subunit protein. The current paper reports structures of RFC/PCNA with two separate DNA molecules, one containing the well characterized 3'-recessed DNA and surprisingly, a second 5'-recessed DNA outside the central chamber. The paper is an important addition to understanding RFC function, particularly in DNA repair. https://doi.org/10.7554/eLife.77469.sa0 Decision letter Reviews on Sciety eLife's review process Introduction All three domains of life possess a DNA clamp and clamp loader that are essential for cell growth and proliferation (Bell and Labib, 2016; Yao and O’Donnell, 2016). The clamp and clamp loader function in genomic DNA replication, DNA damage repair, and other DNA metabolic processes (Burgers and Kunkel, 2017; Harrison and Haber, 2006; Ohashi and Tsurimoto, 2017; Sancar et al., 2004; Su, 2006; Waga and Stillman, 1998). The eukaryotic PCNA clamp and its clamp loader complex are key components of the replisome (Ellison and Stillman, 2001; Hedglin et al., 2013; Hingorani and O’Donnell, 2000; Indiani and O’Donnell, 2006; Yao and O’Donnell, 2012; Yao and O’Donnell, 2016; Zhang and O’Donnell, 2016). PCNA needs to be cracked open by a clamp loader to encircle the genomic DNA because it is a topologically closed ring. The eukaryotic clamp loader is Replication Factor C (RFC), composed of Rfc1-5, belonging to a large family of proteins involved in diverse cellular activities, referred to as the AAA+ (ATPases Associated with various cellular Activities) family (Figure 1a; Cullmann et al., 1995; Davey et al., 2002; Miller and Enemark, 2016; Snider et al., 2008). The ATP sites of AAA + oligomers, many of which are used in DNA replication, are located at subunit interfaces (Erzberger and Berger, 2006), including the bacterial and eukaryotic RFC clamp loaders (Bowman et al., 2004; Jeruzalmi et al., 2001). Interfacial ATP sites makes possible the coordination among subunits during hydrolysis and, in fact, recent deep mutagenesis of a clamp loader pentamer reveals a communication network among subunits needed to achieve the clamp loading reaction (Subramanian et al., 2021). Figure 1 with 4 supplements see all Download asset Open asset Cryo-EM captured multiple S.c. RFC–(PCNA)–DNA complexes. (a) Domain architecture of RFC, PCNA, and the template/primer DNA. Dashed lines indicate unsolved regions. AL is the alternative linker between Rfc1 AAA+ and collar domain. Pink line between PCNA NTD and CTD represents the inter-domain connecting loop (IDCL). DNA used in this study harbors both 5′-DNA and 3′-DNA junctions. (b) Sketch illustrating the previously established DNA1 binding site recognizing the 3′-DNA junction in the RFC central chamber (left) and the novel 5′-DNA2 site recognizing the 5′-DNA junction on Rfc1 shoulder. (c) 3D maps of the five loading intermediates: RFC–3′-DNA1 and RFC–3′-DNA1–5′-DNA2 (left), RFC–3′-DNA1–PCNA in closed and open spiral form (middle), and RFC–3′-DNA1–5′-DNA2–PCNA (right). These maps are displayed at the same threshold (0.2). RFC is in orange, PCNA pink. DNA strands are individually colored. Structural studies on clamp loaders of E. coli, T4 phage, yeast, and human have revealed a conserved architecture of a five-subunit spiral with two tiers (Bowman et al., 2004; Gaubitz et al., 2020; Kelch et al., 2011; Simonetta et al., 2009). The upper tier is a sealed ring consisting of five collar domains - one from each subunit, whereas the lower tier is composed of five AAA+ modules and is an open spiral with a gate between the first and the fifth subunits. However, the first subunit of the eukaryotic and T4 phage clamp loaders contain an additional A’ domain at their respective C termini that contacts the fifth subunit and closes the spiral gap (Kelch et al., 2012b). The five ATP binding sites are located at the interfaces between adjacent subunits, with one subunit contributing the Walker A (P-loop) and Walker B (DExx box, where the x can be any residue) motifs, and the other contributing the SRC motif that harbors an essential ‘arginine finger’ residue (Johnson et al., 2006). All studies thus far have revealed that primer/template (P/T) DNA with a 3′-recessed end binds inside the chamber of the ATP-bound clamp loader (Figure 1b; Bowman et al., 2005; Kelch et al., 2011). Moreover, clamp loaders of bacterial and eukaryotic systems only need ATP binding to crack open the clamp ring; neither ATP hydrolysis nor DNA is required (Hingorani and O’Donnell, 1998; Kelch et al., 2012b; Kelch et al., 2012a; Turner et al., 1999; Zhuang et al., 2006). DNA binding appears to properly engage the ATPase sites for hydrolysis, leading to closure of the clamp around the duplex and dissociation of the clamp loader from DNA (Anderson et al., 2009; Chen et al., 2009; Gaubitz et al., 2022; Kelch et al., 2012b; Liu et al., 2017; Marzahn et al., 2015; Sakato et al., 2012a; Trakselis et al., 2003). The replication clamps are ring-shaped complexes that encircle dsDNA and slide freely on the duplex, conferring processivity to their respective replicative DNA polymerase (Kunkel and Burgers, 2014; Kunkel and Burgers, 2017; Nick McElhinny et al., 2008; ODonnell and Kurth, 2013; Pursell et al., 2007; Yao and O’Donnell, 2021). In eukaryotes, PCNA (Proliferating Cell Nuclear Antigen) functions with replicative polymerases Pol δ on the lagging strand and Pol ε on the leading stand (Kunkel and Burgers, 2014; Kunkel and Burgers, 2017; Nick McElhinny et al., 2008; ODonnell and Kurth, 2013; Pursell et al., 2007; Yao and O’Donnell, 2021). Structural studies showed that, the E. coli β-clamp is a homodimer, while the T4 phage clamp and archaeal and eukaryotic PCNA clamps are homotrimers, all of which display six domains having similar chain folds and remarkable pseudo sixfold symmetric architecture with an obvious ancestor in evolution (Gulbis et al., 1996; Kong et al., 1992; Krishna et al., 1994; Matsumiya et al., 2001; Yao and O’Donnell, 2016). The monomers are arranged in head-to-tail manner, with 12 α-helices that line the inner cavity and a continuous layer of antiparallel β-sheet forming the outside perimeter, even at the protomer interfaces. In each case, the domains within each monomer are linked by an interdomain connecting loop (IDCL). The diameter of the PCNA inner lumen is about 38 Å, and the inner surface is also basic, thus suitable to encircle a 20 Å wide dsDNA and is shown to slide on DNA freely (Bloom, 2009; Li et al., 2021). PCNA interacts with numerous proteins in replication, repair, and cell cycle control (Kelman, 1997; Maga and Hubscher, 2003). All replication clamps characterized so far mainly interact with their partners by their respective carboxy-terminal ‘front’ faces. The ‘front’ face of each monomer possesses a hydrophobic pocket that interacts with the PIP motif (PCNA-interacting peptide), or modified PIP motifs of clamp interactive proteins (Altieri and Kelman, 2018; Fernandez-Leiro et al., 2015; Gulbis et al., 1996; Lancey et al., 2020; Madru et al., 2020; Prestel et al., 2019; Zheng et al., 2020). A recent cryo-EM study captured yeast RFC in a series of intermediate states during loading of the PCNA clamp onto DNA, including an intermediate in which the PCNA ring is open by 20 Å, sufficiently wide for dsDNA to pass through (Gaubitz et al., 2022). This conformation was not observed in the crystallographic study of the T4 phage clamp−loader−DNA complex (Kelch et al., 2011). The new structure confirms that clamp opening does not need ATP hydrolysis. However, PCNA closure around dsDNA induced conformation changes that tighten up the RFC ATP binding sites at subunit interfaces and likely stimulate the ATPase. ATP hydrolysis presumably releases RFC from PCNA, making PCNA available to bind its functional partners, such as Pols δ and ε for DNA synthesis, and FEN1 and ligase for Okazaki fragment maturation (Bell and Labib, 2016; Yao and O’Donnell, 2016). Rad24-RFC is an alternative clamp loader in which Rad24 replaces Rfc1 of the RFC clamp loader and loads the DNA damage signaling 9-1-1 clamp onto a 5′-recessed DNA end (Ellison and Stillman, 2003; Majka et al., 2006; Majka and Burgers, 2003). We and others recently determined the cryo-EM structures of the Rad24-RFC−9-1-1 clamp complex bound to a 5′-ss/ds DNA (Castaneda et al., 2022; Zheng et al., 2022). We observe two structures in which the 9-1-1 clamp is either closed or had a 27 Å opening. These structures revealed that the 5′-junction DNA is held specifically by the Rad24 subunit in a long basic groove between the AAA+ module and collar domain, and that the 3′ ssDNA overhang enters the inner chamber of the alternative loader. This DNA interaction mode is unexpected, as it is entirely different from the DNA binding pattern of RFC which binds the 3′-recessed dsDNA inside the central chamber, while the 5′ ss/ds DNA is not observed to bind the clamp loader as reported in the T4 phage and yeast structures (Kelch et al., 2011). The surprising location of the 5′-ss/ds DNA binding site on the Rad24 subunit, but outside the central chamber of Rad24-RFC, led us to ask if RFC also contains a second DNA binding site that binds 5′ ss/ds DNA above the clamp ring. If true, the 5′ ss/ds DNA binding site may explain the previously reported 5′-ss/ds DNA junction binding by the human RFC1 BRCT domain (Kobayashi et al., 2010; Kobayashi et al., 2006). In addition, dual binding of 3′ and 5′ recessed DNA ends by RFC suggests that RFC may bind both ends of a DNA gap, congruent with genetic studies demonstrating that mutants in the N-terminal region of Rfc1 are defective in excision gap repair (Aboussekhra et al., 1995; Gomes et al., 2000; Li et al., 1994; McAlear et al., 1996; Shivji et al., 1992). These clues to dual DNA binding sites in RFC have inspired us to examine the structure of S. cerevisiae RFC in the presence of a double-tailed DNA in which both the 3′-recessed and 5′-recessed ends are present on the same molecule. We used this strategy in our previous Rad24-RFC study that revealed 5′ ss/ds end binding to Rad24 (Zheng et al., 2022). Indeed, we found that RFC can bind up to two DNA molecules at the same time, one being the well-established site wherein a recessed 3′ ss/ds DNA binds inside the pentamer central chamber, and a second site that binds a recessed 5′ ss/ds DNA at the Rfc1 “shoulder” region outside the central chamber. This surprising dual DNA site binding mode of RFC described here resembles the DNA binding by Rad24-RFC (Castaneda et al., 2022; Zheng et al., 2022). We also examine the affinity and PCNA clamp loading efficiency of RFC at different sized DNA gaps. The results reveal enhanced RFC binding at 5–50 nt gaps, and 5′ end stimulation in loading of PCNA at a 10-nt gap and 30-nt gap, consistent with a role of RFC 5′ end binding in gap repair. The results also show a measurable enhancement in RFC loading of PCNA at an RPA-coated 30-nt gap, suggesting that RFC may act in longer excision tracks, and possibly binds both 3′ and 5′ ends of an Okazaki fragment fill-in site, perhaps to protect the 5′ end at Okazaki fragments and prevent the DNA damage repair pathway triggered by it. Results RFC can engage a 3′-DNA in the central chamber simultaneously with a 5′-DNA located on the Rfc1 ‘shoulder’ The S. cerevisiae PCNA clamp and RFC clamp loader were separately expressed and purified from E. coli (see Materials and Methods). We assembled the loading complexes in vitro by directly mixing the purified proteins with a double-tailed primer/template DNA with both 3′-recessed and 5′-recessed ends (Figure 1a) in the presence of 0.5 mM slowly hydrolysable ATP analog ATPγS (see details in Materials and Methods). Use of DNA having both 3′ and 5′ ssDNA ends strategically enables the unbiased binding of either end to sites on RFC and 2D classification of cryo-EM images demonstrated the assembly of a variety of loading intermediates, including RFC bound to either one or two DNA molecules, and with the loader either engaged or not with PCNA (Figure 1—figure supplement 1). Subsequent 3D classification and 3D variability analysis (3DVA) led to the capture of five 3D maps: (1) RFC bound to 3′ recessed DNA in the central chamber (termed 3′-DNA1 herein) at 3.3 Å resolution, (2) RFC bound to two DNA molecules at 3.3 Å resolution, with 3′-recessed DNA1 in the central chamber plus a 5′ ss/ds DNA bound to the Rfc1 shoulder (referred to here as 5′-DNA2) (Table 1). The 5′-DNA2 is nearly parallel with and above the position that is occupied by the PCNA ring, (3) RFC-closed planar PCNA with 3′-DNA1 bound in the central chamber and threaded through the PCNA ring at 3.3 Å resolution, (4) RFC-open PCNA with 3′-DNA1 bound in the central chamber and threaded through an open PCNA ring that assumes a right-hand spiral with a 14 Å opening in the clamp at 3.4 Å resolution, and (5) RFC-closed PCNA with 3′-DNA1 in the central chamber plus a molecule of 5′-DNA2 on the Rfc1 shoulder at 3.1 Å resolution (Figure 1c, Figure 1—figure supplements 2–3). The fifth map is a composite map produced by combining the 3.1 Å map of RFC−3′-DNA1−5′-DNA2−PCNA with a locally refined map focusing around Rfc1 NTD (including the BRCT domain and AAA+ module) and 5′-DNA2. Table 1 Cryo-EM data collection, refinement, and atomic model validation. StructuresRFC−3´-DNA1RFC−3´-DNA1−5´-DNA2RFC−3´-DNA1−PCNA (open)RFC−3´-DNA1−PCNA (closed)RFC−3´-DNA1−5´-DNA2−PCNAData collection and processingMagnification105,000Voltage (kV)300Electron dose (e-/Å2)66Under-focus range (μm)1.3–1.9Pixel size (Å)0.828Symmetry imposedC1Initial particle images (no.)1,039,425908,744Final particle images (no.)334,876315,619118,384166,348432,904Map resolution (Å)3.333.253.413.303.09 FSC threshold0.143Map resolution range (Å)2.0–12.02.0–13.02.0–12.02.0–12.02.1–13.0RefinementInitial model used (PDB code)RFC−3´-DNA1−5´-DNA2−PCNA of this study1SXJ, 7SGZ,2K6GMap sharpening B factor (Å2)–93.8–100.8–97.3–118.6–116.6Map to model CCmask0.700.690.820.810.82Model composition Non-hydrogen atoms13,69014,53520,57320,60722,831 Protein and DNA residues1,653; 241,701; 452,480; 422,486; 422,717; 63 Ligands99999R.m.s. deviations Bond lengths (Å)0.0030.0030.0030.0030.003 Bond angels (°)0.6160.6340.5960.6230.562Validation MolProbity score1.721.721.661.561.57 Clashscore9.6010.008.577.597.57 Poor rotamers (%)0.140.130.050.090.04 Ramachandran plot Favored (%)96.6496.7896.8397.2097.14 Allowed (%)3.363.223.172.802.86 Disallowed (%)00000 Interestingly, the RFC structure is highly similar among the five structures captured here, with main chain Cα RMSDs (root-mean-square deviation) ranging from 0.6 Å to 1.0 Å (Figure 1—figure supplement 4, Video 1). In all five structures, the Rfc1 AAA+ module sits above the PCNA protomer (when PCNA is present) at the right side of the DNA entry gate (viewing down from the C-terminal collar), while the Rfc5 AAA+ module is above the PCNA protomer at the left side of the DNA entry gate (Figure 1—figure supplement 4). These structural features are consistent with previous studies (Bowman et al., 2004; Gaubitz et al., 2020; Kelch et al., 2011). The closed-ring PCNA structure of RFC−3′-DNA1−PCNA is comparable with the RFC−PCNA structures determined in the absence of DNA (Bowman et al., 2004; Gaubitz et al., 2020; Figure 1—figure supplement 4). However, DNA makes the structure significantly more compact, as PCNA tilts up by 10° toward RFC, forming a tighter interface (Figure 1—figure supplement 4). In the open PCNA structure, Rfc1 and Rfc5 each bind one different PCNA protomer, holding the two protomers 14 Å apart in-plane and 13 Å apart out-of-plane (Figure 1c, middle panel). Because the 14 Å gap in PCNA is narrower than the 20 Å width of a dsDNA, and 3′-DNA1 is already inside the RFC central chamber, this is likely a post-entry intermediate in which the DNA gate has partially closed. These open and closed PCNA states resemble the open and closed clamp states observed in the T4 phage clamp-clamp loader complex (Kelch et al., 2011) and the recent RFC−PCNA−DNA structure (Gaubitz et al., 2022; Figure 1—figure supplement 4c). Video 1 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as Download as A of the five structures in this The five atomic are around the by by around the These are first to the RFC–3′-DNA1–5′-DNA2–PCNA model by the subunits Rfc1 and and shown separately as in the same as in Figure RFC has been for many and is known to bind recessed 3′-DNA in the central chamber, it has not previously been to also contain a recessed 5′-DNA binding Indeed, studies were on RFC in which the N-terminal region of Rfc1 containing of the 5′-DNA site was et al., 2000; McAlear et al., 1996; et al., is well known that RFC binds PCNA in an ATP et al., 2006), similar to studies of the E. coli clamp-clamp loader interaction that is on et al., We also show here that RFC interacts with DNA either in the absence of PCNA and or in the presence of PCNA spiral PCNA, and ring PCNA, and and This suggests that RFC can interact with DNA of PCNA, which we the of this structure to freely hydrolysable ATP as determined by studies and Burgers, 2001). Figure 2 with 2 supplements see all Download asset Open asset 3′-DNA1 binding conformation changes and of the 5′-DNA2 (a) of RFC–3′-DNA1 complex by subunits and DNA strands in and in in a side (left) and a (right). The Rfc5 the DNA groove is The ATPγS and one at the are in (b) of the five AAA+ domains of RFC in the structure in the absence of DNA (left) or bound to 3′-DNA1 or bound to 3′-DNA1 and 5′-DNA2 domains are for (c) Rfc1 in the absence of DNA (PDB entry is with the AAA+ module with Rfc1 in the presence of 3′-DNA1 large of the collar and A’ domains with the The region in the is in the right showing the changes of the alternative linker the of the AL is shown in The structures in are by Rfc1 and 3′-DNA1 binding induced large changes in RFC that the 5′-DNA2 binding site RFC bound to 3′-DNA1 is in the of a spiral with a closed collar ring on the and an open spiral AAA+ tier on the (Figure The five RFC subunits are arranged from and Rfc5 from the from the C-terminal collar the five binding were occupied by ATPγS and one by Rfc5 and in Figure from the C-terminal domains and of the C-terminal collar is possibly an ATPγS hydrolysis by The Rfc5 subunit contains a that the central chamber. In the absence of the Rfc5 is and is a gap at the ATP binding interface between and in the RFC−PCNA structures in the presence of ATPγS and (Bowman et al., 2004; Gaubitz et al., 2020; Figure In the or structures, the Rfc5 and the groove of 3′-DNA1 located in the central chamber (Figure Figure supplement 1). the domains of 2 and 5 a large of to open a referred to as the (Gaubitz et al., between the AAA+ module and the A’ domain of Rfc1 and to tighten up the interface between and perhaps the ATPase activity at this site (Figure However, the Rfc1 A’ domain 3′-DNA1 and only the the connecting the collar and A’ domains (Figure The 3′-DNA1 binding site in the chamber is in RFC, but the 5′-DNA2 site, located between the collar domain and the AAA+ module of is not in the absence of 3′-DNA1 but it is binding 3′ DNA. the Rfc1 collar region is to its AAA+ module with only a residue two domains (Figure Our structures reveal that, to the of the ring binding as described 3′-DNA1 binding also conformation changes in the to of the Rfc1 AAA+ module and the first of the collar domain. in the second of the AAA+ to and the first residue of the collar and with an This loop the of the Rfc1 collar and A’ leading to the of the (Figure Figure supplement Video We have the loop that forms binding 3′-DNA1 as the because it is of the Rad24 long linker between the AAA+ module and collar domain which the DNA binding at the Rad24 shoulder (Figure 1—figure supplement a recent structural study revealed a similar RFC form induced by ATPγS binding DNA (Gaubitz et al., 2022). Video 2 Download asset This video cannot be played in place because your browser does support HTML5 video. You may still download the video for offline viewing. Download as MPEG-4 Download as Download as of Rfc1 from in the structure to in the structure of The two are by the subunits Rfc1 and and shown first side by side in the is to and to with DNA1 in the two structures are and the PCNA clamp and DNA are for The structures around the by for of the 5′-DNA2 binding The subunits 2 and with the collar lower left to open the gate between the AAA+ module and the A’ domain of Rfc1 DNA1 entry the RFC chamber 1). a large groove is between Rfc1 collar domain and AAA+ module to 5′-DNA2 at its shoulder The Rfc1 BRCT domain in the shoulder 5′-DNA2 binding is also the 3D of from 3D variability analysis two had either 3′-DNA1 or had both 3′-DNA1 and 5′-DNA2 sites occupied Figure 1—figure supplement each for about of the particle The had 3′-DNA1 and partially occupied 5′-DNA2 and for of the However, we not observe an structure in which the 5′-DNA2 site is and the 3′-DNA1 site is on our structural we that RFC binds 3′-DNA1 inside the central chamber and that 3′-DNA1 binding the conformation changes that the 5′-DNA2 binding The Rfc1 BRCT domain 5′-DNA2 binding In the RFC−3′-DNA1−5′-DNA2−PCNA structure, 5′-DNA2 binding the Rfc1 C-terminal domain (Figure The yeast Rfc1 BRCT domain resembles a on an and is composed of a by a long (Figure The the BRCT domain and is similar to the structure of the human RFC1 BRCT domain (Kobayashi et al., 2010; Figure The BRCT contains a β-sheet by three with and at one side and at the other and an additional at the The loop connecting and in our yeast Rfc1 BRCT structure is the of the loop in the human RFC1 BRCT domain. Figure with 1 supplement see all Download asset Open asset The BRCT domain of Rfc1 5′-DNA2 in the RFC–3′-DNA1–5′-DNA2–PCNA (a) The atomic model of the RFC–3′-DNA1–5′-DNA2–PCNA The Rfc1 BRCT domain 5′-DNA2. in the two are in (c) and (b) of the yeast Rfc1 BRCT domain in the of the RFC complex bound to DNA not with the human RFC1 BRCT domain entry The human RFC1 BRCT was to the 5′-junction of dsDNA by the end region of (c) showing between RFC and and of the domain of 4, and 2 around the DNA is shown as with the base and base in strand shown in and the of DNA are in with are in The main chain of and in the of and 2 form with DNA. of the 5′-DNA2 binding The Rfc1 BRCT domain on and AAA+ module from the the 5′-DNA2. 5′-DNA2 are The of Rfc1 collar domain and the 5′-DNA2 The residue located at the and the DNA while to the DNA only structures are the same and is used in all The of 3′-DNA1 and 5′-DNA2 in RFC (left) resembles a DNA (right). RFC with 3′-DNA1 and 5′-DNA2 The RFC interaction with 3′-DNA1 is similar in all five captured 3′-DNA1 is by a series of α-helices in the structure (Figure and of the domains of bind and spiral around the 3′-DNA1 similar to the T4 clamp-clamp loader (Kelch et al., 2011). In the of of and of with the of the the of and in the of Rfc5 also with the of the and the Rfc5 with the The of Rfc1 the groove of the Rfc1 is to the observed in the bacterial β-clamp loader et al., and at the of the from the and the two are by the Rfc1 and In addition, Rfc1 and also with the unwound (Figure base by
Source: eLife
Language: English
Topic: DNA Repair Mechanisms
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,500
OpenAlex ID: W4285738764