The University of Osaka · Biochemistry, Genetics and Molecular Biology
Professor Masatoshi Hara's research lab focuses on the molecular mechanisms governing cell cycle regulation and translational control during early animal development, particularly in the oocyte-to-embryo transition. The lab investigates key regulators such as the PNG kinase complex, M-phase-promoting factor, and kinases like Greatwall, elucidating their roles in cell cycle progression and mRNA translation. Using model systems including Drosophila and starfish, the lab combines biochemistry, cell biology, and live imaging to dissect signaling networks that ensure faithful cell division and developmental transitions. Their work reveals critical post-translational control mechanisms, including phosphorylation-dependent activation and substrate specificity, with implications for developmental biology and human disease.
Figures are computed from collected data and may differ slightly.
Maturation/M-phase-promoting factor is the universal inducer of M-phase in eukaryotic cells. It is currently accepted that M-phase-promoting factor is identical to the kinase cyclin B-Cdk1. Here we show that cyclin B-Cdk1 and M-phase-promoting factor are not in fact synonymous. Instead, M-phase-promoting factor contains at least two essential components: cyclin B-Cdk1 and another kinase, Greatwall kinase. In the absence of Greatwall kinase, the M-phase-promoting factor is undetectable in oocyte
The kinetochore is essential for faithful chromosome segregation during mitosis. To form a functional kinetochore, constitutive centromere-associated network (CCAN) proteins are assembled on the centromere chromatin that contains the centromere-specific histone CENP-A. CENP-C, a CCAN protein, directly interacts with the CENP-A nucleosome to nucleate the kinetochore structure. As CENP-C is a hub protein for kinetochore assembly, it is critical to address how the CENP-A-CENP-C interaction is regul
The Drosophila Pan Gu (PNG) kinase complex regulates hundreds of maternal mRNAs that become translationally repressed or activated as the oocyte transitions to an embryo. In a previous paper (Hara et al., 2017), we demonstrated PNG activity is under tight developmental control and restricted to this transition. Here, examination of PNG specificity showed it to be a Thr-kinase yet lacking a clear phosphorylation site consensus sequence. An unbiased biochemical screen for PNG substrates identified
The oocyte-to-embryo transition involves extensive changes in mRNA translation, regulated in Drosophila by the PNG kinase complex whose activity we show here to be under precise developmental control. Despite presence of the catalytic PNG subunit and the PLU and GNU activating subunits in the mature oocyte, GNU is phosphorylated at Cyclin B/CDK1sites and unable to bind PNG and PLU. In vitro phosphorylation of GNU by CyclinB/CDK1 blocks activation of PNG. Meiotic completion promotes GNU dephospho
A key event in the oocyte-to-embryo transition is the start of the embryonic mitotic cell cycle. Prior to this start, the cell cycle in oocytes is generally arrested at a particular stage during meiosis, and the meiotic arrest is released by fertilization. However, it remains unclear how release from the meiotic arrest is implicated in the start of the embryonic cell cycle. To elucidate this link, we have used starfish eggs, in which G1 phase arrest occurs after completion of meiosis if the matu
The influence of pre-dialysis blood pressure (BP) on the prognosis of hemodialysis (HD) patients is still inconclusive.A total of 3436 HD patients were prospectively followed up for 4 years. The patients were divided into quintiles of pre-dialysis systolic BP (SBP) and diastolic BP (DBP) levels [mm Hg]: Quintile 1 (Q1), SBP <134, DBP <66; Q2, SBP 134 to 147, DBP 66 to 72; Q3, SBP 148 to 158, DBP 73 to 79; Q4, SBP 159 to 171, DBP 80 to 85; Q5, SBP ≥172, DBP ≥86. The association between the pre-di
The kinetochore is a large protein complex that ensures accurate chromosome segregation during mitosis by connecting the centromere and spindle microtubules. One of the kinetochore sub-complexes, the constitutive centromere-associated network (CCAN), associates with the centromere and recruits another sub-complex, the KMN (KNL1, Mis12, and Ndc80 complexes) network (KMN), which binds to spindle microtubules. The CCAN-KMN interaction is mediated by two parallel pathways (CENP-C- and CENP-T-pathway
Establishing the correct kinetochore-microtubule attachment is crucial for faithful chromosome segregation. The kinetochore has various regulatory mechanisms for establishing correct bipolar attachment. However, how the regulations are coupled is not fully understood. Here, we demonstrate a regulatory loop between the kinetochore protein CENP-C and Aurora B kinase, which is critical for the error correction of kinetochore-microtubule attachment. This regulatory loop is mediated through the bindi
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