Functional Characterization Of Proteins Required For Mitotic Progression And The Spindle Assembly Checkpoint

During mitotic cell division, the genetic materials packed into chromosomes is divided equally between two daughter cells. Before the separation of the 2 copies of a chromosome (sister chromatids), each chromosome has to be correctly connected with microtubules of the mitotic spindle apparatus and aligned to the centre of the cell. The spindle assembly checkpoint (SAC) screens connections between microtubules and chromosomes in addition to tension applied throughout the centromere. Microtubules connect with a chromosome through kinetochores, which are proteinaceous organelles assembled onto the centromeric region of the sister chromatids. Improper kinetochore-microtubule attachments activate the SAC and block chromosome segregation till errors are corrected and all chromosomes are linked to the mitotic spindle in a bipolar manner. The objective of this surveillance mechanism is to stop loss or acquire of chromosomes in daughter cells that according to current understanding contributes to most cancers formation. Numerous proteins take part in the regulation of mitotic progression. In this thesis, the mitotic duties of three kinetochore proteins, Shugoshin 1 (Sgo1), INCENP, and p38 MAP kinase (p38 MAPK), had been investigated. Sgo1 is a protector of centromeric cohesion. It can also be described in the pressure-sensing mechanism of the SAC and within the regulation of kinetochore-microtubule connections. Our results revealed a central function for Sgo1 in a novel department of kinetochore meeting. INCENP constitutes a part of the chromosomal passenger complex (CPC). The different members of the core complex are the Aurora B kinase, Survivin and Borealin. CPC is an important regulatory component of cell division having a number of roles at varied phases of mitosis. Our outcomes indicated that INCENP and Aurora B are extremely dynamic proteins on the mitotic centromeres and instructed a brand new position for CPC in regulation of chromosome movements and spindle structure throughout late mitosis. The p38 MAPK has been implicated in G1 and G2 checkpoints through the cell cycle. However, its function in mitotic progression and management of SAC signaling has been controversial. In this thesis, we discovered a novel operate for p38╬│ MAPK in chromosome orientation and spindle construction in addition to in promotion of viability of mitotic cells.