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Vrp1p functions in both actomyosin ring-dependent and Hof1p-dependent pathways of cytokinesis
S N Naqvi1, Q Feng, V J Boulton
1Laboratory of Yeast Cell Biology, Institute of Molecular Agrobiology, 1 Research Link, The National University of Singapore, Singapore 117604, Republic of Singapore. suniti@ima.org.sg
Insights
Verprolin (Vrp1p) is crucial for yeast cell division, impacting cytokinesis and actomyosin ring function. Its loss causes significant delays and defects, particularly at higher temperatures, affecting cell viability.
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.
Abstract:
Vrp1p/verprolin/End5p is a Saccharomyces cerevisiae proline-rich protein, structurally and functionally related to human Wiskott-Aldrich syndrome protein-interacting protein. Vrp1p is required for viability at 37 degrees C, but not 24 degrees C. Here, we show that loss of Vrp1p (vrp1Delta) leads to a 3-4-fold delay in cytokinesis, wide bud necks, abnormal actomyosin rings, and aberrant septa even at 24 degrees C. Like other mutations affecting the actomyosin ring, vrp1Delta is synthetic lethal with deletion of HOF1 (or CYK2), which encodes a protein related to mammalian proline serine threonine phosphatase-interacting protein and Schizosaccharomyces pombe Cdc15p required for an actomyosin ring-independent pathway of cytokinesis in S. cerevisiae. At 37 degrees C, vrp1Delta cells rapidly cease dividing and exhibit a novel terminal phenotype: a single large bud, two well-separated nuclei, and an interphase microtubule array. The arrested cells have a persistent ring containing both actin and myosin at the bud neck. Many also exhibit some polarisation of cortical actin patches to the bud neck. Vrp1p binds an SH3-domain-containing fragment of Hof1p in vitro. Vrp1p is required in vivo for Hof1p relocalisation to a single ring at the bud neck prior to cytokinesis at 37 degrees C, but not at 24 degrees C. Vrp1p thus acts in both actomyosin ring formation and function, as well as in Hof1p localisation during cytokinesis.