| First Author | You Z | Year | 2005 |
| Journal | Nucleic Acids Res | Volume | 33 |
| Issue | 9 | Pages | 3033-47 |
| PubMed ID | 15917436 | Mgi Jnum | J:99444 |
| Mgi Id | MGI:3582148 | Doi | 10.1093/nar/gki607 |
| Citation | You Z, et al. (2005) DNA binding and helicase actions of mouse MCM4/6/7 helicase. Nucleic Acids Res 33(9):3033-47 |
| abstractText | Helicases play central roles in initiation and elongation of DNA replication. We previously reported that helicase and ATPase activities of the mammalian Mcm4/6/7 complex are activated specifically by thymine-rich single-stranded DNA. Here, we examined its substrate preference and helicase actions using various synthetic DNAs. On a bubble substrate, Mcm4/6/7 makes symmetric dual contacts with the 5'-proximal 25 nt single-stranded segments adjacent to the branch points, presumably generating double hexamers. Loss of thymine residues from one single-strand results in significant decrease of unwinding efficacy, suggesting that concurrent bidirectional unwinding by a single double hexameric Mcm4/6/7 may play a role in efficient unwinding of the bubble. Mcm4/6/7 binds and unwinds various fork and extension structures carrying a single-stranded 3'-tail DNA. The extent of helicase activation depends on the sequence context of the 3'-tail, and the maximum level is achieved by DNA with 50% or more thymine content. Strand displacement by Mcm4/6/7 is inhibited, as the GC content of the duplex region increases. Replacement of cytosine-guanine pairs with cytosine-inosine pairs in the duplex restored unwinding, suggesting that mammalian Mcm4/6/7 helicase has difficulties in unwinding stably base-paired duplex. Taken together, these findings reveal important features on activation and substrate preference of the eukaryotic replicative helicase. |
