Dynein collective behavior in mitotic nuclear positioning of Saccharomyces cerevisiae

Positioning the nucleus at the bud-neck prior during Saccharomyces cerevisiae mitosis during anaphase involves pulling forces of cytoplasmic dynein localized in the daughter cell. While genetic analysis has revealed a complex network positioning the nucleus, quantification of the forces acting on th...

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Bibliographic Details
Published inbioRxiv
Main Authors Jain, Kunalika, Khetan, Neha, Palani, Saravanan, Athale, Chaitanya A
Format Paper
LanguageEnglish
Published Cold Spring Harbor Cold Spring Harbor Laboratory Press 23.06.2020
Subjects
Anaphase
Cell membranes
Computer applications
Dynein
Fluorescence microscopy
Genetic analysis
Mitosis
Mobility
Nuclear transport
Saccharomyces cerevisiae
Spindle pole bodies
Yeast
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Summary:Positioning the nucleus at the bud-neck prior during Saccharomyces cerevisiae mitosis during anaphase involves pulling forces of cytoplasmic dynein localized in the daughter cell. While genetic analysis has revealed a complex network positioning the nucleus, quantification of the forces acting on the nucleus and dyneins numbers driving the process has remained difficult. In order to better understand the role of motor-microtubule mechanics during nuclear positioning and the role of dynein, we have used a computational model of nuclear mobility in S. cerevisiae and reconciled it to the mobility of labelled spindle pole bodies (SPBs) measured by quantifying fluorescence microscopy time-series. We model the apparent random-walk mobility of SPBs by combining diffusion of the nucleus and active pushing of MTs at the cell membrane. By minimizing the deviation between tracks of fluorescently tagged SPBs and simulations, we estimate the effective cytoplasmic viscosity to be 0.5 Pa s. The directed transport of nuclei during the budding process is similarly quantified by tracking the daughter SPB (SPB-D) in experiment. Using force-balance, we find 2 to 8 motors are required to pull the nucleus to the bud-neck. Simulations of the cytoplasmic MT (cMT) 'search and capture' by dynein suggest single motor binding is followed by a rapid saturation of number of bound motors. The short time and length of MT interactions with the cortex and minimal collective dynein force required, predict a functional role for dynein clustering in nuclear positioning. Competing Interest Statement The authors have declared no competing interest.
DOI:10.1101/2020.06.23.166769