Human DNA polymerase delta is a pentameric holoenzyme with a dimeric p12 subunit

• DOI: 10.26508/lsa.201900323
• Publication Date: 2019-03-18T18:45:20Z
• Authors: Prashant Khandagale; Doureradjou Peroumal; Kodavati Manohar; Narottam Acharya
• Keywords: DNA Replication; Protein Conformation, alpha-Helical; 0301 basic medicine; 0303 health sciences; DNA Mutational Analysis; Green Fluorescent Proteins; CHO Cells; Transfection; 6. Clean water; Protein Subunits; 03 medical and health sciences; Cricetulus; HEK293 Cells; Protein Domains; Proliferating Cell Nuclear Antigen; Schizosaccharomyces; Animals; Humans; Protein Interaction Domains and Motifs; Schizosaccharomyces pombe Proteins; Protein Multimerization; Holoenzymes; Research Articles; DNA Polymerase III; Protein Binding

Human DNA polymerase delta (Polδ), a holoenzyme consisting of p125, p50, p68, and p12 subunits, plays an essential role in DNA replication, repair, and recombination. Herein, using multiple physicochemical and cellular approaches, we found that the p12 protein forms a dimer in solution. In vitro reconstitution and pull down of cellular Polδ by tagged p12 substantiate the pentameric nature of this critical holoenzyme. Furthermore, a consensus proliferating nuclear antigen (PCNA) interaction protein motif at the extreme carboxyl-terminal tail and a homodimerization domain at the amino terminus of the p12 subunit were identified. Mutational analyses of these motifs in p12 suggest that dimerization facilitates p12 binding to the interdomain connecting loop of PCNA. In addition, we observed that oligomerization of the smallest subunit of Polδ is evolutionarily conserved as Cdm1 ofSchizosaccharomyces pombealso dimerizes. Thus, we suggest that human Polδ is a pentameric complex with a dimeric p12 subunit, and discuss implications of p12 dimerization in enzyme architecture and PCNA interaction during DNA replication.