Studies on PCNA loading onto newly synthesized leading DNA by Ctf18-RFC/Pole complex

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04743
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Molecular biology
• Research Institution: Kyushu University
• Principal Investigator: Tsurimoto Toshiki 九州大学, 理学研究院, 教授 (30163885)
• Co-Investigator(Kenkyū-buntansha): 大橋 英治 九州大学, 理学研究院, 助教 (90378951)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: DNA複製 / 複製フォーク / DNAポリメラーゼ

Outline of Final Research Achievements

This research aimed to study the mechanism to load PCNA on leading- and lagging-strands coordinately during replication in eukaryotes. I have studied the interaction between the second PCNA loader Ctf18-RFC and the leading strand DNA polymerase Pol ε. I elucidated that Ctf18-RFC actively loads PCNA only when it complexes with DNA polymerase ε. Furthermore, these two complexes together exhibit a stable DNA synthesis through a cycle of [DNA synthesis by Pol ε－PCNA] -> [Stalling of the DNA synthesis] -> [PCNA loading by Ctf18-RFC] -> [Restart of DNA synthesis by Pol ε－PCNA－Ctf18-RFC]. This result indicated that Ctf18-RFC is involved in the leading-strand DNA polymerase complex and actively loads PCNA on the leading strands. Considering the role of RFC for loading of PCNA on the lagging strands, RFC and Ctf18-RFC will coordinate PCNA loading on both strands and play a role to distinguish DNA polymerases for syntheses of the two DNA strands.

Free Research Field

分子生物学、生化学

Academic Significance and Societal Importance of the Research Achievements

真核生物染色体複製のDNA伸長の従来のモデルでは明らかになっていなかったリーディング鎖側への複製クランプPCNAの装着機構について、第2のPCNA装着因子Ctf18-RFCが能動的に機能することを明らかにした。さらにこの因子とリーディング鎖合成DNAポリメラーゼPolεが複合体を形成し、常時DNA合成状況をモニターして、合成が停止するたびに速やかにPCNAを装着するしくみがあることを新たに示した。以上は安定な染色体複製を行うためのより実態に近い機構を明らかにしたものと考える。