B56-PP2A regulates motor dynamics for mitotic chromosome alignment

J Cell Sci. 2014 Nov 1;127(Pt 21):4567-73. doi: 10.1242/jcs.154609. Epub 2014 Sep 1.

Abstract

Proper alignment of duplicated chromosomes at the metaphase plate involves both motor-driven chromosome movement and the functional and physical end-on connection (K-fiber formation) between the kinetochore and the plus-end of microtubules. The B56 family of protein phosphatase 2A (PP2A) regulatory subunits (B56-PP2A), through their interaction with the mitotic checkpoint protein BUBR1, are required for proper chromosome alignment, but the underlying mechanism(s) has remained elusive. Here, we show that B56-PP2A promotes chromosome alignment primarily by balancing chromosome movement towards the metaphase plate, rather than by directly establishing stable K-fibers. Notably, the poleward movement of chromosomes in cells depleted of the B56 family can be rescued by depletion of HSET (also known as kinesin-14 or KIFC1), a major minus-end-directed motor protein. Strikingly, K-fiber formation can be restored if chromosome movement to the metaphase plate is rescued in B56-depleted cells. Furthermore, the B56-BUBR1 interaction is required for promoting motor-driven chromosome movement towards the metaphase plate. Thus, we propose that B56-PP2A functions in mitotic chromosome alignment by balancing chromosome movement towards the metaphase plate, which is essential for the subsequent establishment of stable and functional kinetochore-microtubule attachments, and mitotic exit.

Keywords: BUBR1; Chromosome congression; Kinesin; Mitosis; PP2A.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromosomes, Human / genetics
  • Chromosomes, Human / metabolism*
  • HeLa Cells
  • Humans
  • Immunoblotting
  • Kinesin / genetics
  • Kinesin / metabolism*
  • Mitosis / genetics
  • Mitosis / physiology*
  • Protein Binding / genetics
  • Protein Binding / physiology
  • Protein Phosphatase 2 / genetics
  • Protein Phosphatase 2 / metabolism*
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism

Substances

  • KIFC1 protein, human
  • PPP2R5A protein, human
  • BUB1 protein, human
  • Protein-Serine-Threonine Kinases
  • Protein Phosphatase 2
  • Kinesin