Research Projects

Single molecule tracking of Mitotic Cancer therapy target

Single molecule tracking of Cancer therapy target Polo like Kinase I

OBJECTIVES

To quantify the single-molecule dynamics of Cdc5 during various stages of mitosis.
Single molecule tracking of Cdc5 during meiosis I and meiosis II.
Single molecule tracking of Plk1 in healthy and cancerous human cells.

Introduction:

Polo-like kinases (Plks) are a group of serine-threonine phosphorylases that serve essential mitotic functions such as mitotic entry and exit, chromosome segregation, bipolar spindle formation, centrosome maturation and cytokinesis. They are conserved from yeast to humans and their impaired functions lead to severe chromosome missegregation, aneuploidy, and cancers. Overexpression of Plk1 is positively correlated with aggressiveness and prognosis in many cancers. Plk1 is overexpressed in several cancers such as lung cancer, head and neck cancer, esophageal and gastric cancer, melanomas, breast cancer, ovarian cancer, endometrial cancer, colorectal cancer, gliomas, thyroid cancer. Therefore, Plk1 is being used as a novel diagnostic marker for several types of cancers, and inhibition of Plk1 function could be an important application for cancer therapy.

In yeast S. cerevisiae, Cdc5 is a single essential polo-like kinase, homologous to human Plk1, which provides a valuable tool for studying its specific function. Like Plk1, Cdc5 phosphorylates its many substrates in a coordinated manner by changing its localization during the cell cycle . Cytoplasmic Cdc5 promotes mitotic entry in G1, then it is imported to the nucleus in G2/M to promote mitotic entry and phosphorylates cohesin subunit Scc1. During anaphase, Cdc5 helps in spindle elongation and releasing Cdc14 phosphatase for mitotic exit. In late anaphase, Cdc5 is released from the nucleus to the cytoplasm to phosphorylate its cytoplasmic late anaphase substrate Bfa1 to activate second mitotic exit pathway . Cdc5 accumulates at the bud neck in late anaphase to promote cytokinesis. Apart from its cell-cycle dependent nuclear-cytoplasmic relocation, Cdc5 also localizes to the Spindle-Pole Bodies (SPBs) from S-phase until the end of mitosis . Apart from its mitotic functions, Cdc5 is also considered as a central regulator of meiosis I. It phosphorylates a cohesin subunit Rec8 that leads to its cleavage for the metaphase I to anaphase I transition. It also promotes degradation of Spo13 during meiosis II for releasing the protection of the centromeric cohesin, however, its kinase activity is dispensable for this cause. We are planned to depict this dynamicity of Plk-1 using Single molecule tracking.