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Distinct but overlapping domains of AKAP95 are implicated in chromosome condensation and condensin targeting

Turid Eide, Cathrine Carlson, Kristin A Taskén, Tatsuya Hirano, Kjetil Taskén, Philippe Collas

Author Affiliations

  1. Turid Eide1,
  2. Cathrine Carlson1,
  3. Kristin A Taskén1,
  4. Tatsuya Hirano2,
  5. Kjetil Taskén1 and
  6. Philippe Collas (philippe.collas{at}basalmed.uio.no)*,1
  1. 1 Institute of Medical Biochemistry, University of Oslo, PO Box 1112, Blindern, N‐0317, Oslo, Norway
  2. 2 Cold Spring Harbor Laboratory, PO Box 100, Cold Spring Harbor, NY, 11724, USA
  1. * Tel: +47 22851066; Fax: +47 22851058; E‐mail: philippe.collas{at}basalmed.uio.no

Abstract

A‐kinase (or PKA)‐anchoring protein AKAP95 is a zinc‐finger protein implicated in mitotic chromosome condensation by acting as a targeting molecule for the condensin complex. We have identified determinants of chromatin‐binding, condensin‐targeting and chromosome‐condensation activities of AKAP95. Binding of AKAP95 to chromatin is conferred by residues 387–450 and requires zinc finger ZF1. Residues 525–569 are essential for condensation of AKAP95‐free chromatin and condensin recruitment to chromosomes. Mutation of either zinc finger of AKAP95 abolishes condensation. However, ZF1 is dispensable for condensin targeting, whereas the C‐terminal ZF2 is required. AKAP95 interacts with Xenopus XCAP‐H condensin subunit in vitro and in vivo but not with the human hCAP‐D2 subunit. The data illustrate the involvement of overlapping, but distinct, domains of AKAP95 for condensin recruitment and chromosome condensation and argue for a key role of ZF1 in chromosome condensation and ZF2 in condensin targeting. Moreover, condensin recruitment to chromatin is not sufficient to promote condensation.

  • Received November 22, 2001.
  • Revision received February 18, 2002.
  • Accepted March 1, 2002.