8UN0
Atomic model of the human CTF18-RFC-PCNA-DNA ternary complex with cracked and closed PCNA (state 7)
Summary for 8UN0
| Entry DOI | 10.2210/pdb8un0/pdb |
| EMDB information | 42389 |
| Descriptor | Chromosome transmission fidelity protein 18 homolog, PHOSPHOTHIOPHOSPHORIC ACID-ADENYLATE ESTER, ADENOSINE-5'-DIPHOSPHATE, ... (11 entities in total) |
| Functional Keywords | dna clamp loader complex, replication-dna complex, replication/dna |
| Biological source | Homo sapiens (human) More |
| Total number of polymer chains | 10 |
| Total formula weight | 372978.24 |
| Authors | |
| Primary citation | He, Q.,Wang, F.,O'Donnell, M.E.,Li, H. Cryo-EM reveals a nearly complete PCNA loading process and unique features of the human alternative clamp loader CTF18-RFC. Proc.Natl.Acad.Sci.USA, 121:e2319727121-e2319727121, 2024 Cited by PubMed Abstract: The DNA sliding clamp PCNA is a multipurpose platform for DNA polymerases and many other proteins involved in DNA metabolism. The topologically closed PCNA ring needs to be cracked open and loaded onto DNA by a clamp loader, e.g., the well-studied pentameric ATPase complex RFC (RFC1-5). The CTF18-RFC complex is an alternative clamp loader found recently to bind the leading strand DNA polymerase ε and load PCNA onto leading strand DNA, but its structure and the loading mechanism have been unknown. By cryo-EM analysis of in vitro assembled human CTF18-RFC-DNA-PCNA complex, we have captured seven loading intermediates, revealing a detailed PCNA loading mechanism onto a 3'-ss/dsDNA junction by CTF18-RFC. Interestingly, the alternative loader has evolved a highly mobile CTF18 AAA+ module likely to lower the loading activity, perhaps to avoid competition with the RFC and to limit its role to leading strand clamp loading. To compensate for the lost stability due to the mobile AAA+ module, CTF18 has evolved a unique β-hairpin motif that reaches across RFC2 to interact with RFC5, thereby stabilizing the pentameric complex. Further, we found that CTF18 also contains a separation pin to locally melt DNA from the 3'-end of the primer; this ensures its ability to load PCNA to any 3'-ss/dsDNA junction, facilitated by the binding energy of the E-plug to the major groove. Our study reveals unique structural features of the human CTF18-RFC and contributes to a broader understanding of PCNA loading by the alternative clamp loaders. PubMed: 38669181DOI: 10.1073/pnas.2319727121 PDB entries with the same primary citation |
| Experimental method | ELECTRON MICROSCOPY (3 Å) |
Structure validation
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