Both sickle cell disease and β-thalassemia are major sources of morbidity and mortality worldwide. Continued production of the β-like γ-globin genes that form fetal hemoglobin after infancy has been ...shown to ameliorate the severity of these disorders. As a result, there has been considerable interest in understanding the underlying regulation of the physiologic fetal-to-adult hemoglobin switch in humans to be able to better manipulate this process for therapeutic purposes. To date, only a single factor, BCL11A, has been identified as being involved in the developmental regulation of human hemoglobin switching. BCL11A is a direct transcriptional repressor of the γ-globin genes. Moreover, BCL11A is expressed in a developmental stage-specific manner to regulate human hemoglobin switching. However, despite extensive studies, the mechanisms that act upstream to regulate BCL11A expression and thereby control hemoglobin switching have remained elusive. To gain further insights, we have directly explored the developmental regulation of BCL11A expression at various stages of human erythropoiesis. We find that BCL11A is regulated at the level of mRNA translation during development. While BCL11A mRNA is comparably expressed in a similar manner at all developmental stages in erythroid cells, robust protein expression only occurs in adult erythroid cells. Importantly, we demonstrate that at the earlier stages of development, the observed reduction in protein expression is attributable to decreased synthesis and not increased degradation of BCL11A through direct assessment of both protein synthesis and degradation rates in primary erythroid cells from various stages of human development. Interestingly, while BCL11A protein is not well synthesized at these earlier stages of development, we find that its mRNA curiously continues to be associated with ribosomes in a comparable manner between newborn and adult erythroid precursors using polysome fractionation of stage-matched erythroid cells. Through use of an unbiased proteomic analysis approach involving RNA affinity purification of the 18S ribosomal RNA in erythroid cells, we demonstrate that the RNA-binding protein LIN28B, which is developmentally expressed in a reciprocal pattern to BCL11A, directly interacts with ribosomes. We additionally show that the observed suppression of BCL11A protein translation is mediated by LIN28B. Using a newly developed RNA isolation and crosslinking immunoprecipitation approach coupled to massively parallel sequencing we mapped the direct interaction of LIN28B with BCL11A mRNA at nucleotide resolution. Through a number of functional assays in both newborn and adult erythroid cells, we additionally demonstrate that this alteration of BCL11A translation is entirely independent of the role of LIN28B in the biogenesis of let-7 microRNAs. Finally, we show that BCL11A is the major functional target in LIN28B-mediated fetal hemoglobin induction through functional complementation experiments in primary human erythroid cells. Our results reveal a previously unappreciated regulatory mechanism underlying human hemoglobin switching. Moreover, our findings highlight opportunities for developing improved treatments for sickle cell disease and β-thalassemia by understanding the upstream regulation of human hemoglobin switching.
No relevant conflicts of interest to declare.
In order to investigate the effect of inlet splitter on pressure fluctuations in a double-suction centrifugal pump, three research schemes, including no splitter (scheme I), a splitter along the flow ...passage centerline (scheme II) and a splitter above the flow passage centerline in the suction (scheme III), were designed. The flow in the pump was simulated by commercial code FLUENT. The viscous Navier-Stokes equations were handled with an unsteady calculation and the sliding mesh technique was applied to take into account the impeller-volute interaction. Based on the simulation results, the hydraulic performance and pressure fluctuations were obtained and analyzed in detail. The hydraulic performance agrees well with the experimental results. The pressure fluctuations under three schemes are different. The maximum amplitude of the pressure fluctuations in scheme II is the minimum. For monitoring points near volute tongue, rotating frequency and its harmonies are dominant under three research schemes. The maximum amplitude of pressure fluctuations of three schemes are all at the blade passing frequency. In particular, the maximum pressure fluctuation amplitude of scheme II was less than that of scheme I and scheme III, which illustrated that it is effective to reduce the peak value of pressure fluctuations in double suction centrifugal pump by installing a splitter in the suction properly.
Individuals chronically infected with hepatitis C virus (HCV) commonly exhibit hepatic intracellular lipid accumulation, termed steatosis. HCV infection perturbs host lipid metabolism through both ...cellular and virus-induced mechanisms, with the viral core protein playing an important role in steatosis development. We have recently identified a liver protein, the cell death-inducing DFFA-like effector B (CIDEB), as an HCV entry host dependence factor that is downregulated by HCV infection in a cell culture model. In this study, we investigated the biological significance and molecular mechanism of this downregulation. HCV infection in a mouse model downregulated CIDEB in the liver tissue, and knockout of the CIDEB gene in a hepatoma cell line results in multiple aspects of lipid dysregulation that can contribute to hepatic steatosis, including reduced triglyceride secretion, lower lipidation of very-low-density lipoproteins, and increased lipid droplet (LD) stability. The potential link between CIDEB downregulation and steatosis is further supported by the requirement of the HCV core and its LD localization for CIDEB downregulation, which utilize a proteolytic cleavage event that is independent of the cellular proteasomal degradation of CIDEB.
Our data demonstrate that HCV infection of human hepatocytesin vitroandin vivoresults in CIDEB downregulation via a proteolytic cleavage event. Reduction of CIDEB protein levels by HCV or gene editing, in turn, leads to multiple aspects of lipid dysregulation, including LD stabilization. Consequently, CIDEB downregulation may contribute to HCV-induced hepatic steatosis.
In order to investigate the effect of the guide vane outlet angle on the performance of centrifugal pumps, a centrifugal pump with guide vanes was used as the research model and its specific speed is ...165. Keep all the other geometry parameters of the pump as constants, the guide vane outlet angle was designed to be 28°, 20°, 15°,10°, 5° and 3° respectively. The whole flow field in the pump under different guide vane outlet angles was simulated by commercial code CFX and the simulation was unsteady. The simulation results were validated by experiment results. According to the simulations, the hydraulic performance, internal flow and radial force of the pump under different guide vane outlet angles were compared and analyzed in detail. The research results indicate that the head and efficiency of the pump are the best when the guide vane outlet angle is 10°. With the decrease of the blade outlet angle of guide vane, the length of flow channels in the guide vane become bigger and its width gets smaller, the uniformity of inner flow in the centrifugal pump gets better, and therefore the radial force on the impeller reduces. With the decrease of the guide vane blade outlet angle, the pulsation frequency of radial force does not change, but the pulsation amplitude of the radial force reduces obviously. The vector distribution of the unsteady radial force is symmetric around the origin and mainly lies in 5 regions, which is same as the blade number of impeller.
Hepatitis B virus (HBV) chronically infects an estimated 300 million people, and standard treatments are rarely curative. Infection increases the risk of liver cirrhosis and hepatocellular carcinoma, ...and consequently, nearly 1 million people die each year from chronic hepatitis B. Tools and approaches that bring insights into HBV biology and facilitate the discovery and evaluation of antiviral drugs are in demand. Here, we describe a method to initiate the replication of HBV, a DNA virus, using synthetic RNA. This approach eliminates contaminating background signals from input virus or plasmid DNA that plagues existing systems and can be used to study multiple stages of HBV replication. We further demonstrate that this method can be uniquely applied to identify sequence variants that confer resistance to antiviral drugs.
An optimization method for the hydraulic design of centrifugal pumps at multi-operation points was proposed by means of a global optimization algorithm and a computational model for estimating ...hydraulic losses and energy performance of centrifugal pumps. In the method, the values of several key geometric parameters in an original design were used as the initial conditions, and the design head was considered as a constraint condition, and the weighted average shaft-power at multiple operation conditions was chosen as the objective function. The adaptive simulated annealing algorithm was used to solve the model of hydraulic losses and energy performance. Additionally, the super-transitive approximation method was applied to update optimal weighted coefficients in the objective function. A centrifugal pump with a special speed of 129.3 was optimized with the method. The CFD numerical simulations were done for the original design and the optimized one, respectively. It was shown that the shaft-power of the optimi
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