Biology subjects

Tsukada, K.

Publications and source records attributed to Tsukada, K..

3 recordsLinked to original sources

bioRxiv2025

DDIAS is a single-stranded DNA-binding effector of the TOPBP1-CIP2A complex in mitosis

DNA double-strand breaks and unresolved DNA replication intermediates are particularly dangerous during mitosis. Paradoxically, cells inactivate canonical DNA repair mechanisms during chromosome segregation in favor of alternative pathways that depend on TOPBP1 and CIP2A, but how they function is still poorly defined. Here, we describe the identification of DDIAS as a mitosis-specific DNA damage response protein. We establish DDIAS as a phosphorylation-dependent component and effector of the TOPBP1-CIP2A complex with single-stranded DNA (ssDNA)-binding activity, and thereby delineate a ssDNA protection mechanism that safeguards chromosome integrity during mitosis, particularly in BRCA-deficient cells. We also identify biallelic inactivating mutations in DDIAS in a patient with a severe neurodevelopmental disorder. These findings highlight for the first time a potential physiological role for the DNA damage response in mitosis.

molecular biology↗

bioRxiv2025

Visualization of the microstructure and distribution of follicles in deep human ovaries using speckle-modulated optical coherence microscopy

Ovarian tissue cryopreservation (OTC) and transplantation (OTT) are the only fertility preservation (FP) options for children, adolescents, and young adults (CAYA) who dont enough time until treatment of primary disease. OTC is still unestablished FP options, but it is expected that selective preservation of ovarian tissue with high follicle density will enhance pregnancy efficiency. Despite its value as a noninvasive follicle visualization method, optical coherence microscopy (OCM) lacks sufficient spatial resolution, imaging depth, and noise suppression capabilities to resolve fine follicular structures in deep ovarian tissue. In this study, we applied speckle modulation to a wavelength-swept OCM optical system in the near-infrared region to visualize the fine structure of follicles distributed in deep tissues. OCM images of 4-day-old mice revealed dense superficial-layer distributions of primordial follicles. These follicles were distinguishable from primary follicles, which were surrounded by a single layer of granulosa cells. In 14-day-old ovarian tissue, secondary follicles exhibited spatial dominance, and the fine structures constituting the follicles were successfully visualized. In ovarian tissues extracted from a patient diagnosed with acute myeloid leukemia (AML), the fine structures of primordial follicles were visualized to a depth of 300 m, and a comparison with HE staining revealed that follicle density varied significantly depending on the ovarian regions. Speckle modulation-assisted OCM visualized the microstructure of follicles with varying degrees of maturation in human ovaries at the depth necessary for clinical application. Overall, this technology enables quantitative ovarian reserve assessment and selective cryopreservation of ovarian tissue rich in immature follicles, supporting FP in CAYA diagnosed with cancer.

bioengineering↗

bioRxiv2021

Phosphorylation of PNKP mediated by CDKs promotes end-processing of Okazaki fragments during DNA replication

Polynucleotide kinase phosphatase (PNKP) has enzymatic activities as 3' -phosphatase and 5' - kinase of DNA ends to promote DNA ligation and repair. Here, we show that cyclin-dependent kinases (CDKs) regulate the phosphorylation of threonine 118 (T118) in PNKP. This phosphorylation allows recruitment to the gapped DNA structure found in single-strand DNA nicks and/or gaps between Okazaki fragments (OFs) during DNA replication. T118A (alanine)-substituted PNKP-expressing cells exhibited accumulation of single-strand DNA gaps in S phase and accelerated replication fork progression. Furthermore, PNKP is involved in poly (ADP-ribose) polymerase 1 (PARP1)-dependent replication gap filling as a backup pathway in the absence of OFs ligation. Altogether, our data suggest that CDK-mediated PNKP phosphorylation at T118 is important for its recruitment to single-strand DNA gaps to proceed with OFs ligation and its backup errors via the gap-filling pathway to maintain genome stability.

molecular biology↗