DNA binding properties of human Cdc45 suggest a function as molecular wedge for DNA unwinding
Overview of Szambowska A et al.
| Authors | Szambowska A Tessmer I Kursula P Usskilat C Prus P Pospiech H Grosse F |
|---|---|
| Affiliation | Research Group Biochemistry Leibniz Institute for Age Research -Fritz Lipmann Institute Beutenbergstrasse 11 D-07745 Jena Germany Laboratory of Molecular Biology IBB PAS Affiliated with University of Gdansk Wita Stwosza 59 Gdansk Poland Rudolf Virchow Center DFG Research Center for Experimental Biomedicine Josef Schneider Strasse 2 7080 Wurzburg Germany Department of Biochemistry Oulu P.O. Box 3000 University of Oulu Oulu 90014 Finland Department of Chemistry University of Hamburg/DESY Notkestrasse 85 22607 Hamburg Germany Biocenter Oulu P.O. Box 3000 University of Oulu Oulu 90014 Finland and Center for Molecular Biomedicine Friedrich-Schiller University Biochemistry Department Jena Germany. |
| Journal | Nucleic Acids Res |
| Year | 2013 |
Abstract
The cell division cycle protein 45 (Cdc45) represents an essential replication factor that, together with the Mcm2-7 complex and the four subunits of GINS, forms the replicative DNA helicase in eukaryotes. Recombinant human Cdc45 (hCdc45) was structurally characterized and its DNA-binding properties were determined. Synchrotron radiation circular dichroism spectroscopy, dynamic light scattering, small-angle X-ray scattering and atomic force microscopy revealed that hCdc45 exists as an alpha-helical monomer and possesses a structure similar to its bacterial homolog RecJ. hCdc45 bound long (113-mer or 80-mer) single-stranded DNA fragments with a higher affinity than shorter ones (34-mer). hCdc45 displayed a preference for 3' protruding strands and bound tightly to single-strand/double-strand DNA junctions, such as those presented by Y-shaped DNA, bubbles and displacement loops, all of which appear transiently during the initiation of DNA replication. Collectively, our findings suggest that hCdc45 not only binds to but also slides on DNA with a 3'-5' polarity and, thereby acts as a molecular 'wedge' to initiate DNA strand displacement.