Tatsunosuke Tomita

By Tatsunosuke Tomita and Yoshiaki Onishi

Circadian rhythms that function in behaviour and physiology have adaptive significance for living organisms from bacteria to humans and reflect the presence of a biological clock. The engine of circadian rhythms is a transcription-translation feedback loop that is fine-tuned by epigenetic regulation in higher eukaryotes. We elucidated the chromatin structure of the Bmal1 gene, a critical component of the mammalian clock system, and have continued to investigate transcriptional regulation including DNA methylation. Various ailments including metabolic diseases can disrupt circadian rhythms, and many human diseases are associated with altered DNA methylation. Therefore, regulated circadian rhythms are important for human health. Here, we summarise the importance of epigenetic clock gene regulation, including DNA methylation of the Bmal1 gene, from the viewpoint of relationships to diseases.

Part of the book: Chromatin and Epigenetics

By Ryo Nishihara, Kazuki Niwa, Tatsunosuke Tomita and Ryoji Kurita

This chapter describes the design of an imidazopyrazinone-type luciferin named as HuLumino1 by us and investigation of its luminescence properties. This luciferin was designed to generate bioluminescence by human serum albumin (HSA) rather than by luciferase derived from luminous organisms. HuLumino1 was developed by modifying a methoxy-terminated alkyl chain to the C-6 position and eliminating a benzyl group at the C-8 position of coelenterazine. To clarify the basis of light emission by HSA, the detailed kinetic properties of the HuLumino1/HSA pair were investigated using a calibrated luminometer. The enzymatic oxidation of HuLumino1 was observed only in the presence of HSA. Results of HSA quantification experiments using HuLumino1 agreed with less than 5% differences with those of enzyme-linked immunosorbent assays, suggesting HuLumino1 could be used for quantitative analysis of HSA levels in serum samples without any pretreatments. These results demonstrate the advantages of the coelenterazine analogue as a bioluminescence reagent to detect non-labeled proteins, which generally do not function as enzymes.

Part of the book: Bioluminescence