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J. Cell Biol.,
Volume 141, Number 3, May 4, 1998 703-713
* Marine Biological Laboratory, Woods Hole, Massachusetts; We have used local fluorescence photoactivation to mark the lattice of spindle microtubules during anaphase A in Xenopus extract spindles. We find
that both poleward spindle microtubule flux and
anaphase A chromosome movement occur at similar
rates (~2 µm/min). This result suggests that poleward
microtubule flux, coupled to microtubule depolymerization near the spindle poles, is the predominant
mechanism for anaphase A in Xenopus egg extracts. In
contrast, in vertebrate somatic cells a "Pacman" kinetochore mechanism, coupled to microtubule depolymerization near the kinetochore, predominates during
anaphase A. Consistent with the conclusion from fluorescence photoactivation analysis, both anaphase A
chromosome movement and poleward spindle microtubule flux respond similarly to pharmacological perturbations in Xenopus extracts. Furthermore, the pharmacological profile of anaphase A in Xenopus extracts differs from the previously established profile for
anaphase A in vertebrate somatic cells. The difference
between these profiles is consistent with poleward microtubule flux playing the predominant role in
anaphase chromosome movement in Xenopus extracts,
but not in vertebrate somatic cells. We discuss the possible biological implications of the existence of two distinct anaphase A mechanisms and their differential
contributions to poleward chromosome movement in
different cell types.
Department of Biochemistry and Biophysics, University of
California, San Francisco, California; § Department of Biology, University of North Carolina, Chapel Hill, North Carolina; and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts
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