An endogenous protein inhibitor, YjhX (TopI), for topoisomerase I from Escherichia coli

2015 Fiscal Year Final Research Report

• Project/Area Number: 26892025
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Applied microbiology
• Research Institution: Osaka City University
• Principal Investigator: Yamaguchi Yoshihiro 大阪市立大学, 複合先端研究機構, 特任准教授(テニュアトラック) (00737009)
• Project Period (FY): 2014-08-29 – 2016-03-31
• Keywords: 応用微生物 / バイオテクノロジー / 生化学 / 分子生物学

Outline of Final Research Achievements

Here, I found a novel, previously unidentified TA system in Escherichia coli named yjhX-yjhQ. Induction of YjhX (85 amino acid residues) causes cell-growth arrest resulting in cell death, while YjhQ (181 residues) co-induction resumes cell growth. The primary cellular target of YjhX was found to be topoisomerase I (TopA), inhibiting both DNA replication and RNA synthesis. Notably, YjhX has no homology to any other toxins of the TA systems. YjhX was expressed well with an N-terminal protein S (PrS) tag in soluble forms. PrS-YjhX specifically interacts with the N-terminal region of TopA (TopA67) but not full-TopA in the absence of plasmid DNA, while PrS-YjhX binds to full-TopA in the presence of DNA. Notably, YjhX does not directly interact with DNA and RNA. YjhX inhibits only topoisomerase I but not topoisomerase III and IV in vitro. Hence, yjhX is renamed as the gene for the topoisomerase I inhibitor (the topI gene). TopI is the first protein inhibitor specific for topoisomerase I.

Free Research Field

応用微生物