Crystal Structure of the Human Pol ? B Subunit in Complex with the C-terminal Domain of the Catalytic Subunit.

ABSTRACT: In eukaryotic DNA replication, short RNA-DNA hybrid primers synthesized by primase-DNA polymerase ? (Prim-Pol ?) are needed to start DNA replication by the replicative DNA polymerases, Pol ? and Pol ?. The C terminus of the Pol ? catalytic subunit (p180C) in complex with the B subunit (p70) regulates the RNA priming and DNA polymerizing activities of Prim-Pol ?. It tethers Pol ? and primase, facilitating RNA primer handover from primase to Pol ?. To understand these regulatory mechanisms and to reveal the details of human Pol ? organization, we determined the crystal structure of p70 in complex with p180C. The structured portion of p70 includes a phosphodiesterase (PDE) domain and an oligonucleotide/oligosaccharide binding (OB) domain. The N-terminal domain and the linker connecting it to the PDE domain are disordered in the reported crystal structure. The p180C adopts an elongated asymmetric saddle shape, with a three-helix bundle in the middle and zinc-binding modules (Zn1 and Zn2) on each side. The extensive p180C-p70 interactions involve 20 hydrogen bonds and a number of hydrophobic interactions resulting in an extended buried surface of 4080 Å(2). Importantly, in the structure of the p180C-p70 complex with full-length p70, the residues from the N-terminal to the OB domain contribute to interactions with p180C. The comparative structural analysis revealed both the conserved features and the differences between the human and yeast Pol ? complexes.

SUBMITTER: Suwa Y 

PROVIDER: S-EPMC4505502 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature