Histone chaperone Nap1 dismantles an H2A/H2B dimer from a partially unwrapped nucleosome

DNA translocases, such as RNA polymerases, inevitably collide with nucleosomes on eukaryotic chromatin. Upon these collisions, histone chaperones are suggested to facilitate nucleosome disassembly and re-assembly. In this study, by performing in vitro transcription assays and molecular simulations, we found that partial unwrapping of a nucleosome by an RNA polymerase dramatically facilitates an H2A/H2B dimer dismantling from the nucleosome by Nucleosome Assembly Protein 1 (Nap1). Furthermore, the results uncovered molecular mechanisms of Nap1 functions in which the highly acidic C-terminal flexible tails of Nap1 contribute to the H2A/H2B binding by associating with the binding interface buried and not accessible to Nap1 globular domains, supporting the penetrating fuzzy binding mechanism seemingly shared across various histone chaperones. These findings have broad implications for the mechanisms by which histone chaperones process nucleosomes upon collisions with translocases in transcription, histone recycling and nucleosomal DNA repair

Bach1 ノックアウトマウスは加齢性および実験的変形性関節症の症状を軽減する

広島大学(Hiroshima University)博士(医学)Doctor of Philosophy in Medical Sciencedoctora

INFLUENCE OF LATERAL TRUNK TILT ON THROWING ARM KINETICS DURING BASEBALL PITCHING

The purpose of this study was to investigate the relationship between lateral trunk tilt angle and several injury-related kinetic parameters during pitching. Based on kinematic data of 12 overhand and three-quarter-hand pitchers, several pitching motions with different lateral trunk tilt angles from the original were simulated. Joint kinetics among the simulated motions was compared. As a result, elbow medial force and elbow varus torque were generally increased as the lateral trunk tilt increased, that is the greater contra-lateral side-bending to the throwing arm side. On the other hand, the shoulder shear force was decreased as the lateral trunk tilt increased. Data from the study demonstrated that the shoulder proximal force was irrelevant to the trunk tilt angle

The lane-switch mechanism for nucleosome repositioning by DNA translocase

Translocases such as DNA/RNA polymerases, replicative helicases, and exonucleases are involved in eukaryotic DNA transcription, replication, and repair. Since eukaryotic genomic DNA wraps around histone octamers and forms nucleosomes, translocases inevitably encounter nucleosomes. A previous study has shown that a nucleosome repositions downstream when a translocase collides with the nucleosome. However, the molecular mechanism of the downstream repositioning remains unclear. In this study, we identified the lane-switch mechanism for downstream repositioning with molecular dynamics simulations and validated it with restriction enzyme digestion assays and deep sequencing assays. In this mechanism, after a translocase unwraps nucleosomal DNA up to the site proximal to the dyad, the remaining wrapped DNA switches its binding lane to that vacated by the unwrapping, and the downstream DNA rewraps, completing downstream repositioning. This mechanism may have broad implications for transcription through nucleosomes, histone recycling, and nucleosome remodeling

Modeling of DNA binding to the condensin hinge domain using molecular dynamics simulations guided by atomic force microscopy

The condensin protein complex compacts chromatin during mitosis using its DNA-loop extrusion activity. Previous studies proposed scrunching and loop-capture models as molecular mechanisms for the loop extrusion process, both of which assume the binding of double-strand (ds) DNA to the hinge domain formed at the interface of the condensin subunits Smc2 and Smc4. However, how the hinge domain contacts dsDNA has remained unknown. Here, we conducted atomic force microscopy imaging of the budding yeast condensin holo-complex and used this data as basis for coarse-grained molecular dynamics simulations to model the hinge structure in a transient open conformation. We then simulated the dsDNA binding to open and closed hinge conformations, predicting that dsDNA binds to the outside surface when closed and to the outside and inside surfaces when open. Our simulations also suggested that the hinge can close around dsDNA bound to the inside surface. Based on these simulation results, we speculate that the conformational change of the hinge domain might be essential for the dsDNA binding regulation and play roles in condensin-mediated DNA-loop extrusion

Bafilomycin A1-sensitive pathway is required for the maturation of cystic fibrosis transmembrane conductance regulator

AbstractCystic fibrosis (CF) is the most common lethal genetic disease in Caucasians caused by the trafficking defects of CF transmembrane conductance regulator (CFTR), which is a cAMP-dependent Cl− channel at the plasma membrane. The trafficking pathway of CFTR is thought to be non-conventional because CFTR maturation is inhibited by the dysfunction of syntaxin 13, which is involved in protein recycling via endosomal pathway. In this study, to clarify whether the endosomal trafficking is required for CFTR maturation, we utilized a specific vacuolar H+-ATPase inhibitor, bafilomycin A1 (BafA1), which inhibits the protein trafficking from early endosome. Our data showed that low concentration of BafA1 (50nM) decreased the expression of mature CFTR but induced the accumulation of immature CFTR in the juxta-nuclear region containing an early endosome marker. Pulse-chase analysis showed that BafA1 inhibited the maturation of CFTR, but it slightly stabilized immature CFTR. These results indicate that BafA1-sensitive pathway is required for CFTR maturation and emphasize that endosomal trafficking pathway might be involved in the maturation of CFTR

Status of Nanosatellite Development for Mothership Daughtership Space Experiment by Japanese Universities

We have begun the feasibility study to build a small satellite in the 3kg mass range and in the power range less than 30W since October in 1998, sponsored by National Space Development Agency of Japan (NASDA). This satellite installs three reaction wheels for an attitude control and camera which will demonstrate optical navigation experiment by using image processing. The BBM design status is described in this paper. The components such as a small reaction wheel, electric flash and onboard computer were built. Mothership - daughtership technology and formation flying experiments are planned. New electric propulsion is being developed for small satellite

The Role of Sonic Hedgehog Signaling in Osteoclastogenesis and Jaw Bone Destruction.

Sonic hedgehog (SHH) and its signaling have been identified in several human cancers, and increased levels of its expression appear to correlate with disease progression and metastasis. However, the role of SHH in bone destruction associated with oral squamous cell carcinomas is still unclear. In this study we analyzed SHH expression and the role played by SHH signaling in gingival carcinoma-induced jawbone destruction. From an analysis of surgically resected lower gingival squamous cell carcinoma mandible samples, we found that SHH was highly expressed in tumor cells that had invaded the bone matrix. On the other hand, the hedgehog receptor Patched and the signaling molecule Gli-2 were highly expressed in the osteoclasts and the progenitor cells. SHH stimulated osteoclast formation and pit formation in the presence of the receptor activator for nuclear factor-κB ligand (RANKL) in CD11b+ mouse bone marrow cells. SHH upregulated phosphorylation of ERK1/2 and p38 MAPK, NFATc1, tartrate-resistant acid phosphatase (TRAP), and Cathepsin K expression in RAW264.7 cells. Our results suggest that tumor-derived SHH stimulated the osteoclast formation and bone resorption in the tumor jawbone microenvironment

Characteristics of macroalgal vegetation along the coasts of Yashiro and Heigun islands, western Seto Inland Sea, Japan : especially, on the vertical distribution patterns of species of Sargassum and Ecklonia

瀬戸内海西部の伊予灘と広島湾の島嶼（屋代島，平郡島）で，大型褐藻のホンダワラ類（ヒバマタ目ホンダワラ科）とクロメ（コンブ目レッソニア科）により形成される藻場の特性を調べた。対象とした藻場は，自然岩礁域およびそれに付帯する礫集積域に形成されているものが8か所，投石による人工礁に形成されているものが3か所であり，ライントランセクト法により植生の垂直構造を明らかにし，そこにみられる法則性と環境要因との関係について考察した。調査では計85種の海藻を確認し，そのうちホンダワラ類についてはヒジキ，ノコギリモク，アカモク，ジョロモク，ホンダワラ等の計14種をみとめた。総じて，ホンダワラ類は潮間帯から水深4m 程度までで優占し，クロメは14mを下限にホンダワラ類より深所まで分布した。しかし，平郡島南岸や屋代島南岸では，浅所の岩盤上部にクロメ，その下部の漂砂影響域や礫集積域にホンダワラ類が生育し，植生の垂直構造が逆転している場合もみとめられた。人工礁上では，おおむね自然岩礁・礫集積域と類似した植生が形成されていたが，特に屋代島北岸（広島湾側）では深所で沈積浮泥の影響がみとめられ，クロメの生育は不良であるか植生から欠落していた。藻場の環境特性と植生の関係を解析した結果，平均水深が浅い藻場ではホンダワラ類の平均被度が大きくなり，海底傾斜が大きい藻場ではクロメの平均被度が大きくなる傾向がみとめられた。Characteristics of macroalgal beds composed of sargassaceous plants (Fucales, Phaeophyta) and Ecklonia kurome (Laminariales, Phaeophyta) were surveyed at Yashiro and Heigun islands in the western Seto Inland Sea (Iyo-nada Sea and Hiroshima Bay areas). The surveyed macroalgal beds were located on 8 natural rocky or boulder shores and 3 subtidal stone-built artificial reefs. A transect was set at each bed between the upper and lower limits of the macroalgal vegetation to investigate vertical distribution patterns of the constituent species. Eighty-five macroalgal species were recognized in total, and among those, 14 sargassaceous species, such as Sargassum fusiforme, S. macrocarpum, S. horneri, S. fulvellum and Myagropsis myagroides, were found. In general, sargassaceous plants were dominant from the intertidal to 4 m depth, and E. kurome distributed in deeper zones than sargassaceous plants, down to 14 m at the deepest. However, in some beds on the southern coasts of the islands, this vertical pattern was reversed. Ecklonia grows on rocky substrata which was stable and free from the effects of sand action, though sargassaceous plants grow on boulders distributed in zones deeper than the Ecklonia zones. On artificial reefs, similar vegetation with those on natural substrata was established. On reefs of the northern coast of Yashiro Is. (Hiroshima Bay area), however, sedimentation on substrata prevented the growth of Ecklonia. In the correlation analysis between physical characteristics and vegetation of the beds, there is a tendency that mean coverage of sargassaceous plants of the beds is higher as the mean depth of the beds becomes shallower, and that mean coverage of Ecklonia is higher as the slope of the beds becomes steeper.本現地調査は，農林水産省プロジェクト研究「地球温暖化が水産分野に与える影響評価と適応技術の開発」（平成22―24年度）および水産庁「藻場・干潟の炭素吸収源評価と吸収機能向上技術の開発」（平成23，24年度）の一環として実施し，とりまとめにあたってはJSPS科研費25450267の助成を受けたものである

Inhibition of post-translational N-glycosylation by HRD1 that controls the fate of ABCG5/8 transporter

N-glycosylation of proteins in endoplasmic reticulum is critical for protein quality control. We showed here a post-translational N-glycosylation affected by the HRD1 E3 ubiquitin ligase. Both WT- and E3-defective C329S-HRD1 decreased the level of high mannose form of ABCG8, a protein that heterodimerizes with ABCG5 to control sterol balance. Meanwhile, HRD1 increased the non-glycosylated ABCG8 regardless of its E3 activity, thereby suppressing full maturation of ABCG5/8 transporter. Pulse chase and mutational analysis indicated that HRD1 inhibits STT3B-dependent post-translational N-glycosylation of ABCG8. Whereas, HRD1 had only slight effect on the N-glycosylation status of ABCG5; rather it accelerated ABCG5 degradation in an E3 activity-dependent manner. Finally, RMA1, another E3 ubiquitin ligase, accelerated the degradation of both ABCG5 and ABCG8 via E3 activity-dependent manner. HRD1 and RMA1 may therefore be negative regulators of disease-associated transporter ABCG5/ABCG8. The findings also highlight the unexpected E3 activity-independent role of HRD1 in the regulation of N-glycosylation