Vrp1p functions in both actomyosin ring-dependent and Hof1p-dependent pathways of cytokinesis

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Verprolin (Vrp1p) is a proline-rich protein in Saccharomyces cerevisiae, homologous to human Wiskott-Aldrich syndrome protein-interacting protein.
• Vrp1p is essential for cell viability at 37°C but not at 24°C.

Purpose of the Study:

• To investigate the role of Vrp1p in yeast cell division, specifically cytokinesis and actomyosin ring dynamics.
• To elucidate the relationship between Vrp1p and Hof1p during cytokinesis.

Main Methods:

• Analysis of vrp1Δ mutant phenotypes at different temperatures (24°C and 37°C).
• Assessment of cytokinesis, bud neck morphology, and actomyosin ring structure.
• Investigating synthetic lethality with hof1Δ mutation.
• In vitro binding assays and in vivo localization studies of Vrp1p and Hof1p.

Main Results:

• Loss of Vrp1p (vrp1Δ) causes delayed cytokinesis, wide bud necks, abnormal actomyosin rings, and aberrant septa even at 24°C.
• vrp1Δ is synthetically lethal with hof1Δ, indicating functional overlap in cytokinesis pathways.
• At 37°C, vrp1Δ cells arrest with a distinct terminal phenotype, including a persistent actin-myosin ring at the bud neck.
• Vrp1p binds Hof1p in vitro and is required for Hof1p localization to the bud neck at 37°C.

Conclusions:

• Vrp1p plays a critical role in both the formation and function of the actomyosin ring during cytokinesis.
• Vrp1p is essential for the proper localization of Hof1p to the bud neck, particularly at elevated temperatures.
• These findings highlight Vrp1p's multifaceted involvement in ensuring accurate cell division in S. cerevisiae.