Proper RPA acetylation promotes accurate DNA replication and repair.

The single-stranded DNA (ssDNA) binding protein complex RPA plays a critical role in promoting DNA replication and multiple DNA repair pathways. However, how RPA is regulated to achieve its functions precisely in these processes remains elusive. Here, we found that proper acetylation and deacetylation of RPA are required to regulate RPA function in promoting high-fidelity DNA replication and repair. We show that yeast RPA is acetylated on multiple conserved lysines by the acetyltransferase NuA4 upon DNA damage. Mimicking constitutive RPA acetylation or blocking its acetylation causes spontaneous mutations with the signature of micro-homology-mediated large deletions or insertions. In parallel, improper RPA acetylation/deacetylation impairs DNA double-strand break (DSB) repair by the accurate gene conversion or break-induced replication while increasing the error-prone repair by single-strand annealing or alternative end joining. Mechanistically, we show that proper acetylation and deacetylation of RPA ensure its normal nuclear localization and ssDNA binding ability. Importantly, mutation of the equivalent residues in human RPA1 also impairs RPA binding on ssDNA, leading to attenuated RAD51 loading and homologous recombination repair. Thus, timely RPA acetylation and deacetylation likely represent a conserved mechanism promoting high-fidelity replication and repair while discriminating the error-prone repair mechanisms in eukaryotes.

Study on acoustic radiation force of an elastic sphere in an off-axial Gaussian beam using localized approximation.

In this paper, the expansion coefficients of the off-axial Gaussian beam are obtained using the localized approximation and the translational addition theorem for spherical wave function. The three-dimensional acoustic radiation force of a sphere positioned in an off-axial Gaussian beam is derived. The axial acoustic radiation force of a rigid sphere is computed to verify the derived expressions. The effect of the position of a polystyrene sphere in an off-axial Gaussian beam on the transverse and axial acoustic radiation forces is studied to explore the changing law of particle acoustic manipulation using a Gaussian beam. The calculated results show that the axial force repels the polystyrene particle away from the center of the beam. However, for the transverse force, there is a negative acoustic radiation force at some positions, which is related to the position of the polystyrene sphere in the Gaussian beam, and the negative transverse forces usually pull the polystyrene particle toward the beam axis. In addition, the numerical simulations based on the finite element method are presented to validate the analytical theory, and the comparison results are in good agreement with each other. The study may provide a theoretical basis for the development of single-beam acoustic tweezers using a Gaussian beam.

Acoustic scattering by a finite-length elastic elliptical cylinder in a plane wave.

In this paper, based on the deformed cylinder method, the expression of the far-field acoustic scattering form function of a finite-length elastic elliptical cylinder is obtained. The target strength of elastic aluminum and polymethylmethacrylate (PMMA) elliptical cylinders, with different lengths varying with dimensionless frequency ka, is studied for different incident angles. In addition, the change of the target strength of a PMMA elliptical cylinder with incident angle is explored theoretically and experimentally when the frequency range is 20-40 kHz. Simulation results show that there is almost no change in the peak of the curve of the backscattering target strength versus frequency for a finite-length elastic elliptical cylinder with different lengths. As the length decreases, the target strength gradually decreases. When the theoretical simulation results are compared with the experimental results, it is found that the theoretical predictions are in good agreement with the experimental results. Furthermore, the study will provide theoretical and experimental basis for the prediction and recognition of underwater targets.

Analysis of acoustic radiation force on a rigid sphere in a fluid-filled cylindrical cavity with an abruptly changed cross-section.

This paper studies the acoustic radiation force of a rigid sphere positioned in a fluid-filled cylindrical cavity with an abruptly changed cross-section. This cavity consists of a semi-infinite front tube and a coaxially connected semi-infinite rear tube with different cross-sectional area through a transverse planar junction. Considering a plane wave propagates along the cavity, the exact expression of the acoustic radiation force exerted on the sphere in the front tube is deduced. The effects of the distance between the sphere and the planar junction and the radius ratio of the front tube to the rear tube on acoustic radiation force are analyzed. Numerical results show that the distance influences the acoustic radiation force periodically. Both the distance and the radius ratio of the tubes affect the magnitude and the direction of acoustic radiation force. A finite element model about the calculation for the acoustic radiation force on the sphere in the fluid-filled cylindrical cavity with suddenly changed cross-section is built to validate the theoretical results. The comparison results between the theoretical computation and the finite element simulation are in good agreement with each other. This work can support future studies for the predictive control of a particle in the cavity which has an abruptly changed cross-section.

Axial acoustic radiation force on a spherical particle in a zero-order Mathieu beam.

In this paper, an expression for the acoustic radiation force on a sphere located on the axis of a zero-order Mathieu beam propagating in an ideal fluid is obtained. The simulation results of different kinds of spherical particles, including rigid spheres, fluid spheres, and elastic spheres, are presented to illustrate the theory. Curves of the acoustic radiation force function versus ka are obtained for different half-cone angles ß and ellipticity parameters q of the Mathieu beam. The simulation results reveal that ß and q have a direct effect on the acoustic radiation force exerted on a spherical object in an ideal fluid. The acoustic radiation force has negative values for a fluid sphere in a zero-order Mathieu beam when the half-cone angle is ß≥60°. The value of the half-cone angle ß also affects the direction of the acoustic radiation force for an elastic sphere. When the half-cone angle is set as a constant, the greater the ellipticity parameter is, the slower the decrease in the value of the acoustic radiation force function for a spherical particle. The conclusions of this work may be helpful for the design of acoustic tweezers and may also extend the potential applications of acoustic manipulation technology.

Rapid cell pairing and fusion based on oscillating bubbles within an acoustofluidic device.

Cell fusion is an essential event in many biological processes and has gained increasing attention in the field of biotechnology. In this study, we demonstrate an effective and convenient strategy for cell capture, pairing, and fusion based on oscillating bubbles within an acoustofluidic device. Multirectangular structures of the same size were fabricated at the sidewall of polydimethylsiloxane to generate monodisperse microbubbles. These microbubbles oscillated with a similar amplitude under single-frequency acoustic excitation. Cells were simultaneously captured and paired on the surface of the oscillating bubbles within 40 ms, and the efficiency reached approximately 90%. Homotypic or heterotypic cell membrane fusion was achieved within 15 and 20 min, respectively. More importantly, the homotypic fused cells enabled migration and proliferation at 24 h, indicating that the important biological functions were not altered.

Non-Cavitation Targeted Microbubble-Mediated Single-Cell Sonoporation.

Sonoporation employs ultrasound accompanied by microbubble (MB) cavitation to induce the reversible disruption of cell membranes and has been exploited as a promising intracellular macromolecular delivery strategy. Due to the damage to cells resulting from strong cavitation, it is difficult to balance efficient delivery and high survival rates. In this paper, a traveling surface acoustic wave (TSAW) device, consisting of a TSAW chip and a polydimethylsiloxane (PDMS) channel, was designed to explore single-cell sonoporation using targeted microbubbles (TMBs) in a non-cavitation regime. A TSAW was applied to precisely manipulate the movement of the TMBs attached to MDA-MB-231 cells, leading to sonoporation at a single-cell level. The impact of input voltage and the number of TMBs on cell sonoporation was investigated. In addition, the physical mechanisms of bubble cavitation or the acoustic radiation force (ARF) for cell sonoporation were analyzed. The TMBs excited by an ARF directly propelled cell membrane deformation, leading to reversible perforation in the cell membrane. When two TMBs adhered to the cell surface and the input voltage was 350 mVpp, the cell sonoporation efficiency went up to 83%.

The acoustic radiation force on a multi-layered polymer capsule placed in a fluid-filled tube.

Acoustic manipulation has a series of application in biomedicine, colloidal assembly, and chemistry. A three-layered polymer capsule is generally used structure in manipulation system because it has better protection to the core filled drug or compounds and possesses higher flexibility. In this paper, a theoretical model of acoustic radiation force acting on a three-layered drug capsule in a vessel is established. The acoustic radiation force on a capsule, which comprises of a drug core, a poly(lactide-co-glycolide) mid shell and a chitosan outer shell in the cylindrical tube filled with ideal fluid, is calculated using acoustic wave theory. The influences of the tube, the surrounding fluid and the geometric size of chitosan, poly(lactide-co-glycolide) shell and drug core on acoustic radiation force are investigated. The numerical simulations based on finite element method are introduced to compute the acoustic radiation force and compared with the analytical results. Moreover, the comparison among the capsule in impedance tube, in rigid tube and in unbounded space is obtained simulating specific environment. Simulation results show that the influences of the rigid tube on the acoustic radiation force of the capsule can be ignored when the capsule is much smaller than the radius of the tube. With the increase of the capsule radius, the acoustic radiation force of the capsule changes demonstrably with the frequency and the tube radius because of the influence of the reflective wave resulted from the inner surface of the tube. The properties of the surrounding fluid affect the position of the resonant peaks. Outer radius and mid layer radius have more effects on the acoustic radiation force, but the drug core radius almost exerts no effect on it. The study illustrates that the capsule can be manipulated by acoustic wave with the suitable selection for the outer or mid shell radii, and the selection of drug core radius is of more freedom in this process.

MicroRNA-135b/CAMK2D Axis Contribute to Malignant Progression of Gastric Cancer through EMT Process Remodeling.

There is a continued need for investigating the roles of microRNAs (miRNAs) and their targets on the progression of gastric cancer (GC), especially metastasis. Here, we performed an integrated study to identify dysregulated miRNAs critical for GC development and progression. miR-135b was determined as a promising biomarker for GC. The expression level of miR-135b was increased among GC cell lines, patient tumor tissues, serum samples, and correlation with aggravation of the GC patients. The in vitro functional assays demonstrated overexpression of miR-135b promoted cell proliferation, migration and invasion in GC, while miR-135b inhibition led to the opposite results. CAMK2D was found to be the direct target of miR-135b, serving as a tumor suppressor in GC cells. Based on our and public datasets, we confirmed the attenuation of CAMK2D expression in GC tissues. And, the expression levels of miR-135b and CAMK2D were closely associated with prognosis of GC patients. Ectopic expression of miR-135b resulted in the down-regulation of CAMK2D. Additionally, CAMK2D was a prerequisite for miR-135b to promote GC cells proliferation and migration by regulating the EMT process, which was confirmed by the in vivo experiments. Importantly, in vivo injection of miR-135b antagomir significantly repressed the tumor growth and metastasis of xenograft models, which suggested that the miR-135b antagomir were promising for clinical applications. Taken together, these results indicate that miR-135b/CAMK2D axis drives GC progression by EMT process remodeling, suggesting that miR-135b may be utilized as a new therapeutic target and prognostic marker for GC patients.