Spatial signals link exit from mitosis to spindle position
Jill Elaine Falk,
Dai Tsuchiya,
Jolien Verdaasdonk,
Soni Lacefield,
Kerry Bloom,
Angelika Amon
Affiliations
Jill Elaine Falk
David H Koch Institute for Integrative Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
Dai Tsuchiya
Department of Biology, Indiana University, Bloomington, United States
Jolien Verdaasdonk
Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, United States
Soni Lacefield
Department of Biology, Indiana University, Bloomington, United States
Kerry Bloom
Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, United States
David H Koch Institute for Integrative Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
In budding yeast, if the spindle becomes mispositioned, cells prevent exit from mitosis by inhibiting the mitotic exit network (MEN). The MEN is a signaling cascade that localizes to spindle pole bodies (SPBs) and activates the phosphatase Cdc14. There are two competing models that explain MEN regulation by spindle position. In the 'zone model', exit from mitosis occurs when a MEN-bearing SPB enters the bud. The 'cMT-bud neck model' posits that cytoplasmic microtubule (cMT)-bud neck interactions prevent MEN activity. Here we find that 1) eliminating cMT– bud neck interactions does not trigger exit from mitosis and 2) loss of these interactions does not precede Cdc14 activation. Furthermore, using binucleate cells, we show that exit from mitosis occurs when one SPB enters the bud despite the presence of a mispositioned spindle. We conclude that exit from mitosis is triggered by a correctly positioned spindle rather than inhibited by improper spindle position.
