Researcher ORCID Identifier

0009-0005-9481-7867

Graduation Year

2026

Date of Submission

5-2026

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Aditi Vyas

Reader 2

Patrick Ferree

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Terms of Use for work posted in Scholarship@Claremont.

Rights Information

© 2026 Mason E Spencer

Abstract

Cell cycle dysregulation is a hallmark of cancer, making the molecular mechanisms governing mitotic progression a central focus of cancer biology research. The kinases Dsk1, a serine-arginine protein kinase (SRPK), and Kic1, a LAMMER kinase, regulate the cell cycle in Schizosaccharomyces pombe through phosphorylation of serine/arginine-rich (SR) proteins involved in pre-mRNA splicing. A previous phosphoproteomic study by our lab and collaborators at Peking University identified the kinesin-6 motor protein Klp9 as a direct in vitro substrate of Dsk1. However, in vivo confirmation of this interaction and identification of additional targets remains ongoing. Klp9 drives anaphase B spindle elongation and is the ortholog of human kinesins KIF23 and KIF20B, both of which are overexpressed across multiple cancer types. To extend these in vitro findings to an in vivo context, Klp9-GFP strains were constructed in wild type, Δdsk1, Δkic1, and Δsrp1 S. pombe strains to visualize Klp9-GFP localization via fluorescence microscopy and assess its phosphorylation status and protein level via Western blot analysis. Fluorescence microscopy revealed that a disproportionate number of dividing Δdsk1 cells display Klp9-GFP localized to slanted spindle midzones, suggesting defective Klp9-GFP localization patterns in kinase deletion strains. Western blot analysis demonstrated a statistically significant reduction in Klp9-GFP protein levels in Δdsk1 and a reduction in Δkic1 strains, indicating potential kinase-dependent protein stabilization. Together, these findings suggest that Dsk1 and Kic1 could play a potential role in the phosphorylation status of  Klp9, thus possibly regulating spindle elongation and chromosome separation in mitosis within S. pombe.

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