During interphase, the transport receptor importin-β carries cargoes into the nucleus, where RanGTP releases them. A similar mechanism operates in mitosis to generate a gradient of active spindle assembly factors around mitotic chromosomes. Importin-β and RanGTP have been implicated in additional cellular processes, but the precise roles of the Ran/importin-β pathway throughout the cell cycle remain poorly understood. We implemented a FRET-based, high-throughput small molecule screen for compounds that interfere with the interaction between RanGTP and importin-β and identified importazole, a 2,4-diaminoquinazoline. Importazole specifically blocks importin-β-mediated nuclear import both in Xenopus egg extracts and cultured cells, without disrupting transportin-mediated nuclear import or CRM1-mediated nuclear export. When added during mitosis, importazole impairs the release of an importin-β cargo FRET probe and causes both predicted and novel defects in spindle assembly. Together, these results indicate that importazole specifically inhibits the function of importin-β, likely by altering its interaction with RanGTP. Importazole is a valuable tool to evaluate the function of importin-β/RanGTP pathway at specific stages during the cell cycle.

RCW 120 is a Galactic H II region that has a beautiful ring shape that is bright in the infrared. Our new CO J = 1-0 and J = 3-2 observations performed with the NANTEN2, Mopra, and ASTE telescopes have revealed that two molecular clouds with a velocity separation of 20 km s −1 are both physically associated with RCW 120. The cloud at −8 km s −1 apparently traces the infrared ring, while the other cloud at −28 km s −1 is distributed just outside the opening of the infrared ring, interacting with the H II region as suggested by the high kinetic temperature of the molecular gas and by the complementary distribution with the ionized gas. A spherically expanding shell driven by the H II region is usually considered to be the origin of the observed ring structure in RCW 120. Our observations, however, indicate no evidence of the expanding motion in the velocity space, which is inconsistent with the expanding shell model. We postulate an alternative that, by applying the model introduced by Habe & Ohta, the exciting O star in RCW 120 was formed by a collision between the present two clouds at a collision velocity of ∼30 km s −1 . In the model, the observed infrared ring can be interpreted as the cavity created in the larger cloud by the collision, whose inner surface is illuminated by the strong ultraviolet radiation after the birth of the O star. We discuss that the present cloud-cloud collision scenario explains the observed signatures of RCW 120, i.e., its ring morphology, coexistence of the two clouds and their large velocity separation, and absence of the expanding motion.

High-mass star formation is one of the top-priority issues in astrophysics. Recent observational studies are revealing that cloud-cloud collisions may play a role in high-mass star formation in several places in the Milky Way and the Large Magellanic Cloud. The Trifid Nebula M 20 is a well known galactic Hii region ionized by a single O7.5 star. In 2011, based on the CO observations with NANTEN2 we reported that the O star was formed by the collision between two molecular clouds ∼0.3 Myr ago. Those observations identified two molecular clouds towards M 20, traveling at a relative velocity of 7.5 km s −1 . This velocity separation implies that the clouds cannot be gravitationally bound to M20, but since the clouds show signs of heating by the stars there they must be spatially coincident with it. A collision is therefore highly possible. In this paper we present the new CO J=1-0 and J=3-2 observations of the colliding clouds in M 20 performed with the Mopra and ASTE telescopes. The high resolution observations revealed the two molecular clouds have peculiar spatial and velocity structures, i.e., the spatially complementary distribution between the two clouds and the bridge feature which connects the two clouds in velocity space. Based on a new comparison with numerical models, we find that this complementary distribution is an expected outcome of cloud-cloud collisions, and that the bridge feature can be interpreted as the turbulent gas excited at the interface of the collision. Our results reinforce the cloud-cloud collision scenario in M 20.

The chromosome-centered RanGTP gradient, which is strongly reduced in slow-growing normal cells, is amplified by chromosomal gain and is required for mitosis in rapidly growing aneuploid cells.

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In this paper, we report on an airborne vibrotactile display with a multiunit ultrasound phased array synthetic aperture. The system generates an ultrasound field with a location-tunable focus in the air, which exerts time-variant acoustic radiation pressure on the user's skin, resulting in perceivable localized vibrotactile stimuli. The paper contains three major new contributions from previous related works. The first is an experimental validation of large-aperture focusing with improved synchronization offering an enlarged workspace in which sufficient acoustic power concentration is guaranteed. From the experiments, it is expected that perceivable vibrotactile focus can be generated 1 m away from a four-unit array system. The second is an experimental evaluation of the presented pressure for producing a broad variety of tactile perception, which shows that the generated ultrasound focus can serve as an vibrotactile actuator that has flat frequency characteristics in the domain of perceptual stimuli. The third is a psychophysical result of the detection threshold curve for sinusoidal stimuli offered by the system. The obtained curve shows similarity with conventionally known results, which have minimum values at approximately 200 Hz.

We report a new vibrotactile modulation method of midair ultrasound focus, namely, lateral modulation (LM), in which the focus quickly moves along a small cyclic trajectory and provides stronger and clearer vibrotactile stimuli than those by the conventional amplitude modulation (AM) method. Midair ultrasound haptics has an essential technical advantage of offering remote, non-contact, and pinpoint tactile stimuli on device-free bare skin. On the other hand, lack of clarity in the presented vibrotactile sensation has often been pointed out, and until now, an AM focus has been valid only on glabrous skin. Our main scientific contribution of the article is to verify the LM method, with the following experimental findings newly obtained. We confirmed that with the same maximum output amplitude of the ultrasound phased arrays, LM stimuli with circular focal trajectories were sensed stronger than AM stimuli by glabrous skin and hairy skin in a modulation frequency of 10-200 Hz. We also found that the detection threshold in glabrous skin mainly depended on the focal speed, whereas the tendency in hairy skin was different from that. With these results, we discuss a basis of perceptional mechanism that responds to LM stimuli, along with practical aspects of potential applications.

Cell cycle and DNA repair involve steps requiring RanGTP-regulated nuclear-cytoplasmic transport (NCT). The activation of NCT via overexpression of RCC1 (the guanine nucleotide exchange factor for Ran) accelerated the cell cycle and DNA repair. Normal cells overexpressing RCC1 evaded DNA damage–induced senescence, mimicking cancer cells with high levels of RCC1.