Different assemblies of the DAM1 complex follow shortening microtubules by distinct mechanisms

*Molecular, Cellular, and Developmental Biology Department, University of Colorado, Boulder, CO 80309;
^§National Research Centre for Hematology, Moscow 125167, Russia;
^†Institute of General Pathology and Pathophysiology, Moscow 125315, Russia;
^¶Research Institute of Molecular Pathology, 1030 Vienna, Austria;
^‖Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720;
**Physics Department, Moscow State University, Moscow 119992, Russia; and
^††Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow 119991, Russia

Contributed by J. R. McIntosh, February 24, 2008 (sent for review December 20, 2007)

Abstract

Mitotic chromosomes segregate at the ends of shortening spindle microtubules (MTs). In budding yeast, the Dam1 multiprotein complex supports this dynamic attachment, thereby contributing to accurate chromosome segregation. Purified Dam1 will track the end of a depolymerizing MT and can couple it to microbead transport in vitro. The processivity of such motions has been thought to depend on rings that the Dam1 complex can form around MTs, but the possibility that alternative coupling geometries contribute to these motilities has not been considered. Here, we demonstrate that both rings and nonencircling Dam1 oligomers can track MT ends and enable processive cargo movement in vitro. The coupling properties of these two assemblies are, however, quite different, so each may make a distinct contribution to chromosome motility.

Footnotes

^‡To whom correspondence may be addressed. E-mail: katya{at}colorado.edu or richard.mcintosh{at}colorado.edu
Author contributions: I.S.S. and V.A.V. contributed equally to this work; E.L.G., F.I.A., and J.R.M. designed research; E.L.G., I.S.S., V.A.V., and A.E. performed research; S.W., D.D., and G.B. contributed new reagents/analytic tools; E.L.G., I.S.S., V.A.V., A.E., and F.I.A. analyzed data; and E.L.G. and J.R.M. wrote the paper.
The authors declare no conflict of interest.