Genome-wide analysis reveals novel and discrete functions for tubulin carboxy-terminal tails.
BACKGROUND
Microtubules (MTs) support diverse transport and force generation processes in cells. Both α- and β-tubulin proteins possess carboxy-terminal tail regions (CTTs) that are negatively charged, intrinsically disordered, and project from the MT surface where they interact with motors and other proteins. Although CTTs are presumed to play important roles in MT networks, these roles have not been determined in vivo.


RESULTS
We examined the function of CTTs in vivo by using a systematic collection of mutants in budding yeast. We find that CTTs are not essential; however, loss of either α- or β-CTT sensitizes cells to MT-destabilizing drugs. β-CTT, but not α-CTT, regulates MT dynamics by increasing frequencies of catastrophe and rescue events. In addition, β-CTT is critical for the assembly of the mitotic spindle and its elongation during anaphase. We use genome-wide genetic interaction screens to identify roles for α- and β-CTTs, including a specific role for β-CTT in supporting kinesin-5/Cin8. Our genetic screens also identified novel interactions with pathways not related to canonical MT functions.


CONCLUSIONS
We conclude that α- and β-CTTs play important and largely discrete roles in MT networks. β-CTT promotes MT dynamics. β-CTT also regulates force generation in the mitotic spindle by supporting kinesin-5/Cin8 and dampening dynein. Our genetic screens identify links between α- and β-CTT and additional cellular pathways and suggest novel functions.
Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Jayne
J
Aiken
Department of Biomedical Engineering and Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109, USA.
David
D
Sept
Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5S 3E1, Canada; Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S 3E1, Canada.
Michael
M
Costanzo
Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5S 3E1, Canada; Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S 3E1, Canada.
Charles
C
Boone
Department of Cell Biology and Physiology, Washington University, St. Louis, MO 63110, USA.
John A
JA
Cooper
Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA. Electronic address: jeffrey.moore@ucdenver.edu.
Jeffrey K
JK
Moore
D055106:Genome-Wide Association Study; D008870:Microtubules / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D014404:Tubulin / Q000235:genetics* / Q000378:metabolism
D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin