title: Thermococcus kodakarensis has two functional PCNA homologs but only one is required for viability.
abstract: 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 eukarya and euryarchaea have only one PCNA homolog 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 polymerases B and D and ATP hydrolysis by the replication factor C complex. In exponentially growing cells, PCNA1 is abundant and present at an ~100-fold higher concentration than PCNA2 monomers. Deletion of TK0582 (PCNA2) had no detectable effects on viability or growth whereas repeated attempts to construct a T. kodakarensis strain with TK0535 (PCNA1) deleted were unsuccessful. The implications of these observations for PCNA1 function and the origin of the two PCNA-encoding genes in T. kodakarensis are discussed.
authors.affiliation: Institute for Bioscience and Biotechnology Research, 9600 Gudelsky Drive, Rockville, MD 20850, USA.
authors.forename: Miao
authors.initials: M
authors.lastname: Pan
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Santangelo
authors.forename: Lubomíra
authors.initials: L
authors.lastname: Čuboňová
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Li
authors.forename: Harlette
authors.initials: H
authors.lastname: Metangmo
authors.forename: Jane
authors.initials: J
authors.lastname: Ladner
authors.forename: Jerard
authors.initials: J
authors.lastname: Hurwitz
authors.forename: John N
authors.initials: JN
authors.lastname: Reeve
authors.forename: Zvi
authors.initials: Z
authors.lastname: Kelman
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics* / Q000378:metabolism; D004261:DNA Replication; D017353:Gene Deletion; D050296:Microbial Viability / Q000235:genetics*; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics* / Q000378:metabolism; D055503:Protein Multimerization; D019712:Thermococcus / Q000235:genetics* / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D018809:Proliferating Cell Nuclear Antigen