School of Science Division of Life Science 31 CRISPR/Cas9 Analysis of Essential Genes Supervisor: POON Randy Yat Choi / LIFS Student: SUN Run / BCB Course: UROP1000, Summer Apoptosis is the process of programmed cell death which is critical for cells to survive. Normal cells use this mechanism to clean the body of cells that are irreparable to prevent cancer cells. However, abnormal cells such as cancer cells have deficiency in this function and may grow without control. So, it is indispensable to study the mechanismbehind the process of apoptosis and unveil the essential gene related to it. In this study, we try to uncover the relationship between some relevant genes and MARCH5, a known E3 ubiquitin-protein ligase localized in the mitochondrial outer membrane, and the pathway of how the deficiency of MARCH5 can lead to mitotic cell death in cancer cells. CRISPR/Cas9 Analysis of Essential Genes Supervisor: POON Randy Yat Choi / LIFS Student: ZHOU Siyu / BCB Course: UROP1100, Summer Hypusination is a unique posttranslational modification occurring only on one specific lysine residue of the universal translation factor, eIF5A. The pathway consists of two steps, the first is the processing of eIF5A precursor and spermidine to form deoxyhypusine, which is catalyzed by deoxyhypusine synthase (DHPS), and the second step is completed by deoxyhypusine hydroxylase (DOHH), producing hypusinated, mature eIF5A. While eIF5A, DHPS and DOHH are all essential for cell proliferation, knock out of DHPS causes a band shift of DOHH in Western Blot as observed by Marine Ma in our laboratory (2021). To identify the reason for such change, a recombinant FLAG-tagged DOHH construct was produced, and multiple approaches were adopted to reproduce the result. Targeting Mitotic Regulators in Cancer Cells for Potential Treatment Supervisor: POON Randy Yat Choi / LIFS Student: LIAO Man Kit / CHEM Course: UROP1100, Spring The Spindle Assembly Checkpoint (SAC) and Mitotic Checkpoint Complex (MCC) are important components during mitotic arrest. In the absence of microtubule attachment to kinetochore, a cascade of signal leads to activation of SAC and then the MCC. Inhibition of the Anaphase-Promoting Complex (APC/C) by MCC enables the cells to stay in mitosis. Previous studies suggested that MAD1 is a key component of the SAC and plays a crucial role in this activation of the MCC. Using a conditional system to deplete MAD1, however, indicated that MCC complex can still form and cells can still be arrested in mitosis in the absence of MAD1. These results suggested that MAD1 may not be as crucial for the SAC as once thought.