Sign up for Table of Contents Alerts.

Cell Cycle is published 24 times a year.

Email this page

Print this page

Reports

Protein complexes at the microtubule organizing center regulate bipolar spindle assembly

Adrianna S. Rodriguez, Alison N. Killilea, Joseph Batac, Jason Filopei, Dimitre Simeonov, Ida Lin and Janet L. Paluh

This is an open-access article

 Download PDF

If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.

Bipolar spindle assembly is essential to genomic stability in dividing cells. Centrosomes or spindle pole bodies duplicated earlier at G1/S remain adjacent until triggered at mitotic onset to become bipolar. Pole reorientation is stabilized by microtubule interdigitation but mechanistic details for bipolarity remain incomplete. To investigate the contribution of spindle pole microtubule organizing center (MTOC) proteins in bipolarity, we applied genetic, structural and molecular biochemical analysis along with timelapse microscopy. Spindle formation was followed by an in vivo growth assay with the conditional allele cut7-22ts, encoding fission yeast mitotic Kinesin-5, essential for bipolarity. By analysis of double and triple mutant strains of MTOC alleles and cut7-22ts we found that stabilized microtubules or increased bundling can rescue cut7-22ts associated bipolarity defects. These changes to microtubule dynamics and organization occurred through two surface domains on γ-tubulin, a helix 11 domain and an adjacent site for binding MTOC protein Alp4. We demonstrate that Kinesin-14 Pkl1, known to oppose bipolarity, can bind to γ-tubulin at helix 11 and that mutation of either of two conserved residues in helix 11 can impair Kinesin-14 binding. Altering the Alp4/γ-tubulin interaction, conserved residues in helix 11 or deletion of pkl1 each are sufficient to rescue bipolarity in our cut7-22ts strain. Our findings provide novel insights into regulation of the bipolar mechanism through the MTOC complex.

Authors

Adrianna S. Rodriguez

NYU School of Medicine; New York, NY

Alison N. Killilea

Lawrence Berkeley National Laboratory; Berkeley, CA

Joseph Batac

Tufts University School of Medicine; Boston, MA

Jason Filopei

New York Medical College; Vallhalla, NY

Dimitre Simeonov

Center for Biotechnology & Interdisciplinary Studies; Troy, NY

Ida Lin

Center for Biotechnology & Interdisciplinary Studies; Troy, NY

Janet L. Paluh

Rensselaer Polytechnic Institute

This is an open-access article

 Download PDF

If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.