Biology subjects

Gotoh, T.

Publications and source records attributed to Gotoh, T..

3 recordsLinked to original sources

bioRxiv2025

Acquisition and repeated alteration of (TTGGG)n telomeric repeats in Odonata (dragonflies and damselflies)

Chromosome ends of most eukaryotes are composed of simple telomeric repeats. For arthropods, TTAGG pentanucleotide repeats, (TTAGG)n has been considered as the ancestral telomeric repeat. However, in the order Odonata, the earliest diverged group in insects that contains dragonflies and damselflies, (TTAGG)n signal has been almost undetectable in most examined species. Here, we report a unique pentanucleotide repeat (TTGGG)n as the typical telomeric repeat sequence for Odonata (dragonflies and damselflies). Based on genomic information from ten Odonata species, (TTGGG)n was considered the most likely candidate for telomeric repeat sequences. By fluorescence in situ hybridization (FISH) using 12 Odonata species, clear (TTGGG)n signals were detected at the chromosome ends in both dragonflies and damselflies. By Southern hybridization using 63 Odonata species, strong (TTGGG)n signals were detected from the majority of species covering all three suborders of Odonata, indicating that the telomeric repeat of the common ancestor of extant Odonata is (TTGGG)n. Notably, there were a few Odonata species in which (TTGGG)n signals were faint or absent, suggesting that the telomeric repeat sequence has repeatedly diverged in Odonata, even within genera such as Sympetrum. We also identified telomerase genes in both dragonflies and damselflies, and in some species, more than two telomerase genes are suggested to be present. Overall, this study demonstrates the ancestral acquisition of novel telomeric repeats and their repeated alteration in Odonata.

cell biology↗

bioRxiv2023

Cell viability is dominated by quantum effects

Quantum tunneling is a phenomenon in which small quantum particles pass through a reaction energy barrier, as if they were passing through a tunnel opened in the barrier. In this study, we analyzed the involvement of the quantum tunneling effect in enzymatic chemical reactions involving hydrolysis in vitro, by monitoring the kinetic isotope effects due to hydrogen isotopes and their temperature dependence as indicators. The results demonstrated that the quantum tunneling effect is involved in deacetylation, DNA cleavage, and protein cleavage reactions. These related reactions were also examined in terms of their effects on cells, which revealed that the quantum effect is even involved in cell survival, including the almost complete inhibition of DNA homologous recombinational repair. One-Sentence SummaryDue to quantum effects in numerous enzymatic reactions mediated by hydrolysis, heavy water significantly impacts biological outcomes in cells.

biophysics↗

bioRxiv2018

Distinct control of PERIOD2 degradation and circadian rhythms by the oncoprotein MDM2

The circadian clock relies on post-translational modifications to set the timing for degradation of core regulatory components and, thus, sets clock progression. Ubiquitin-modifying enzymes targeting clock components for degradation are known to mostly recognize phosphorylated substrates. A case in point is the circadian factor PERIOD 2 (PER2) whose phospho-specific turnover involves its recognition by {beta}-transducin repeat containing proteins ({beta}-TrCPs). Yet, the existence of this unique mode of regulation of PER2s stability falls short of explaining persistent oscillatory phenotypes reported in biological systems lacking functional elements of the phospho-dependent PER2 degradation machinery.\n\nIn this study, we challenge the phosphorylation-centric view that PER2 degradation enhances circadian rhythm robustness by i) identifying the PER2:MDM2 endogenous complex, ii) establishing PER2 as a previously uncharacterized substrate for MDM2, iii) revealing an alternative phosphorylation-independent mechanism for PER2 ubiquitin-mediated degradation, iv) pinpointing residues for ubiquitin modification, and v) establishing the importance of MDM2-mediated PER2 turnover for defining the circadian period length. Our results not only expand MDM2s suite of specific substrates beyond the cell cycle to include circadian components but also uncover novel regulatory players that likely impact our view of how other mechanisms crosstalk and modulate the clock itself.

molecular biology↗