Crystal structure of the human Pol? B-subunit in complex with the C-terminal domain of the catalytic subunit.

ABSTRACT: The eukaryotic B-family DNA polymerases include four members: Pol?, Pol?, Pol?, and Pol?, which share common architectural features, such as the exonuclease/polymerase and C-terminal domains (CTDs) of catalytic subunits bound to indispensable B-subunits, which serve as scaffolds that mediate interactions with other components of the replication machinery. Crystal structures for the B-subunits of Pol? and Pol?/Pol? have been reported: the former within the primosome and separately with CTD and the latter with the N-terminal domain of the C-subunit. Here we present the crystal structure of the human Pol? B-subunit (p59) in complex with CTD of the catalytic subunit (p261C). The structure revealed a well defined electron density for p261C and the phosphodiesterase and oligonucleotide/oligosaccharide-binding domains of p59. However, electron density was missing for the p59 N-terminal domain and for the linker connecting it to the phosphodiesterase domain. Similar to Pol?, p261C of Pol? contains a three-helix bundle in the middle and zinc-binding modules on each side. Intersubunit interactions involving 11 hydrogen bonds and numerous hydrophobic contacts account for stable complex formation with a buried surface area of 3094 Å2 Comparative structural analysis of p59-p261C with the corresponding Pol? complex revealed significant differences between the B-subunits and CTDs, as well as their interaction interfaces. The B-subunit of Pol?/Pol? also substantially differs from B-subunits of either Pol? or Pol?. This work provides a structural basis to explain biochemical and genetic data on the importance of B-subunit integrity in replisome function in vivo.

SUBMITTER: Baranovskiy AG 

PROVIDER: S-EPMC5612105 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature