Proliferating cell nuclear antigen (PCNA) monomers assemble to form a ring-shaped clamp complex that encircles duplex DNA. PCNA binding to other proteins tethers them to the DNA providing contacts and interactions for many other enzymes essential for DNA metabolic processes. Most eukaryotes and euryarchaea have only one PCNA homologue but Thermococcus kodakarensis uniquely has two, designated PCNA1 and PCNA2, encoded by TK0535 and TK0582, respectively. Here we establish that both PCNA1 and PCNA2 form homotrimers that stimulate DNA synthesis by archaeal DNA polymerase B (PolB) and ATP hydrolysis by the replication factor C (RFC) complex. In exponentially growing cells, PCNA1 monomers are abundant and present at an ~100-fold higher concentration than PCNA2 monomers. Deletion of TK0582 had no detectable effect on viability or growth whereas repeated attempts to construct a T. kodakarensis strain with TK0535 deleted were unsuccessful. The implications of these observations for PCNA1 function, essentiality and the origin of the two PCNA-encoding genes in T. kodakarensis are discussed.
Citation: Nucleic Acids Research
Pub Type: Journals
archaea, DNA replication, PCNA