Novel insights for the cell cycle developed from analyses of a specific DNA bending factor

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K19233
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 43:Biology at molecular to cellular levels, and related fields
• Research Institution: Kyushu University
• Principal Investigator: Katayama Tsutomu 九州大学, 薬学研究院, 教授 (70264059)
• Project Period (FY): 2021-07-09 – 2024-03-31
• Keywords: DNA複製 / DnaA / DNA屈曲 / 複合体動態 / 細胞周期

Outline of Final Research Achievements

E. coli IHF protein is a DNA bender binding to DNA sequence-specifically. IHF binding supports the initiation of replication at the chromosomal origin, oriC as well as transcription regulation of various genes. DARS2 and datA are chromosomal DNA elements that control the activity of the replication initiation protein DnaA, and are timely activated depending on IHF binding. Before the replication initiation, DARS2 is temporarily activated by IHF binding, activating DnaA. After the replication initiation, datA is temporarily activated by IHF binding, inactivating DnaA. Here, multifaceted analyses were conducted to elucidate the mechanism underlying such controls. As a result, several novel candidate regulators of IHF binding were discovered. In particular, transcription readthrough from the tRNA operon upstream of datA was revealed to sustain timely dissociation of the datA-IHF complex. Multiple transcription termination mechanisms were also revealed to operate within the datA region.

Free Research Field

分子生物学、生化学、分子遺伝学

Academic Significance and Societal Importance of the Research Achievements

datA-IHF複合体は複製開始因子DnaAの活性を抑制する。本研究では、datA-IHF複合体の解離はtRNAオペロンからの転写流入に依存することがわかった。tRNAの転写は細胞増殖が停止する増殖相やアミノ酸枯渇等によりタンパク質合成が阻害される環境（緊縮制御下）では阻害される。このような状況では、tRNAの転写阻害によりdatA-IHF複合体が構成的に形成され、DnaAの不活化を進める、と考えられる。つまり増殖相や環境応答、あるいは転写―翻訳系と連係した複製開始の新たな制御メカニズムが発見された。さらにDARS2-IHF複合体の新たな制御因子候補が見出されたことなども重要な進展と言える。