Biology subjects

Takai, H.

Publications and source records attributed to Takai, H..

4 recordsLinked to original sources

bioRxiv2024

Nobiletin, a Polymethoxyflavonoid, Activates the Desuccinylase Activity of SIRT5 and Prevents the Development of Heart Failure

Nobiletin is a natural compound useful for the prevention and treatment of several diseases. However, the precise role of nobiletin in heart failure is unclear. Nobiletin treatment prevents pressure overload- and myocardial infarction-induced heart failure. Using affinity purification of biotinylated nobiletin from rat heart cell lysates, we identified sirtuin 5 (SIRT5) as a novel nobiletin-binding protein. Nobiletin enhanced the desuccinylase activity of SIRT5 in vitro. Compared to wild-type mice, SIRT5-overexpressing transgenic mice resisted pressure overload-induced systolic dysfunction. Conversely, SIRT5 knockout disrupted the nobiletin-mediated therapeutic effects on heart failure in mice. SIRT5 desuccinylated p300 at lysine 1568 and reduced the histone acetyltransferase (HAT) activity of p300. The desuccinylated p300 mutant suppressed the phenylephrine-induced cardiomyocyte hypertrophic responses. These findings suggest that nobiletin prevents heart failure development through SIRT5-dependent inhibition of p300-HAT activity. Nobiletin, a nontoxic dietary compound, is a potential therapeutic agent for heart failure in humans.

molecular biology↗

bioRxiv2023

CST--Polymeraseα-primase solves a second telomere end-replication problem

Telomerase adds G-rich telomeric repeats to the 3' ends of telomeres1, counteracting telomere shortening caused by loss of telomeric 3' overhangs during leading-strand DNA synthesis ("the end-replication problem"2). We report a second end-replication problem that originates from the incomplete duplication of the C-rich telomeric repeat strand by lagging-strand synthesis. This problem is solved by CST-Polymerase(Pol)-primase fill-in synthesis. In vitro, priming for lagging-strand DNA replication does not occur on the 3 overhang and lagging-strand synthesis stops in an [~]150-nt zone more than 26 nt from the end of the template. Consistent with the in vitro data, lagging-end telomeres of cells lacking CST-Pol-primase lost [~]50-60 nt of CCCTAA repeats per population doubling (PD). The C-strands of leading-end telomeres shortened by [~]100 nt/PD, reflecting the generation of 3 overhangs through resection. The measured overall C-strand shortening in absence of CST-Pol-primase fill-in is consistent with the combined effects of incomplete lagging-strand synthesis and 5' resection at the leading-ends. We conclude that canonical DNA replication creates two telomere end-replication problems that require telomerase to maintain the G-strand and CST-Pol-primase to maintain the C-strand.

cell biology↗

bioRxiv2023

Structural basis of CST-Polα/Primase recruitment and regulation by POT1 at telomeres

Telomere maintenance requires extension of the G-rich telomeric repeat strand by telomerase and fill-in synthesis of the C-rich strand by Pol/Primase. Telomeric Pol/Primase is bound to Ctc1-Stn1-Ten1 (CST), a single-stranded DNA-binding complex. Like mutations in telomerase, mutations affecting CST-Pol/Primase result in pathological telomere shortening and cause a telomere biology disorder, Coats plus (CP). We determined cryogenic electron microscopy structures of human CST bound to the shelterin heterodimer POT1/TPP1 that reveal how CST is recruited to telomeres by POT1. Phosphorylation of POT1 is required for CST recruitment, and the complex is formed through conserved interactions involving several residues mutated in CP. Our structural and biochemical data suggest that phosphorylated POT1 holds CST-Pol/Primase in an inactive auto-inhibited state until telomerase has extended the telomere ends. We propose that dephosphorylation of POT1 releases CST-Pol/Primase into an active state that completes telomere replication through fill-in synthesis.

biophysics↗

bioRxiv2022

Single mutation makes Escherichia coli an insect mutualist

We report an experimental system in which Escherichia coli evolves into an insect mutualist. When the essential gut symbiont of the stinkbug Plautia stali was replaced by E. coli, a few survivor insects exhibited specific localization and vertical transmission of E. coli. Through trans-generational maintenance with P. stali, several hyper-mutating E. coli lines independently evolved hosts high adult emergence and improved body color. Such "mutualistic" E. coli lines exhibited independent mutations disrupting the carbon catabolite repression (CCR) global transcriptional regulator. Each of the mutations reproduced the mutualistic phenotypes when introduced into wild-type E. coli, confirming that the single CCR mutations instantly make E. coli an insect mutualist. Our discovery uncovers that evolution of elaborate mutualism can proceed more easily and rapidly than conventionally envisaged.

evolutionary biology↗