CKAP5 stabilizes CENP-E at kinetochores by regulating microtubule-chromosome attachments.

Stabilization of microtubule plus end-directed kinesin CENP-E at the metaphase kinetochores is important for chromosome alignment, but its mechanism remains unclear. Here, we show that CKAP5, a conserved microtubule plus tip protein, regulates CENP-E at kinetochores in human cells. Depletion of CKAP5 impairs CENP-E localization at kinetochores at the metaphase plate and results in increased kinetochore-microtubule stability and attachment errors. Erroneous attachments are also supported by computational modeling. Analysis of CKAP5 knockout cancer cells of multiple tissue origins shows that CKAP5 is preferentially essential in aneuploid, chromosomally unstable cells, and the sensitivity to CKAP5 depletion is correlated to that of CENP-E depletion. CKAP5 depletion leads to reduction in CENP-E-BubR1 interaction and the interaction is rescued by TOG4-TOG5 domain of CKAP5. The same domain can rescue CKAP5 depletion-induced CENP-E removal from the kinetochores. Interestingly, CKAP5 depletion facilitates recruitment of PP1 to the kinetochores and furthermore, a PP1 target site-specific CENP-E phospho-mimicking mutant gets stabilized at kinetochores in the CKAP5-depleted cells. Together, the results support a model in which CKAP5 controls mitotic chromosome attachment errors by stabilizing CENP-E at kinetochores and by regulating stability of the kinetochore-attached microtubules.

Feedback based gas sensing setup for ppb to ppm level sensing.

Sensing and quantification of gas at low concentrations is of paramount importance, especially with highly flammable and explosive gases such as hydrogen. Standard gas sensing setups have a limit of measuring ultra-low concentrations of few parts per billion unless the external gas cylinders are changed to ones with low concentrations. In this work, we describe a home-built resistance based gas sensing setup that can sense across a wide concentration range, from parts per billion to parts per million, accurately. This was achieved using two dilution chambers: a process chamber and a feedback assembly where a part of the output gas from the dilution chamber is fed back to the inlet mass flow controller, enabling enhanced dilutions without increasing the number of mass flow controllers. In addition, the gas-sensing setup can measure across a large temperature range of 77-900 K. The developed setup was then calibrated using palladium thin films and ZnO nanoparticle thin films. The setup was tested for reproducibility, concentration response, temperature response, etc. Corresponding sensitivity values were calculated and found to be in good agreement with published values, validating our setup design.