KINESIN-RELATED KIP3 OF SACCHAROMYCES-CEREVISIAE IS REQUIRED FOR A DISTINCT STEP IN NUCLEAR MIGRATION

Citation
Tm. Dezwaan et al., KINESIN-RELATED KIP3 OF SACCHAROMYCES-CEREVISIAE IS REQUIRED FOR A DISTINCT STEP IN NUCLEAR MIGRATION, The Journal of cell biology, 138(5), 1997, pp. 1023-1040
Citations number
53
Categorie Soggetti
Cell Biology
Journal title
ISSN journal
00219525
Volume
138
Issue
5
Year of publication
1997
Pages
1023 - 1040
Database
ISI
SICI code
0021-9525(1997)138:5<1023:KKOSIR>2.0.ZU;2-I
Abstract
Spindle orientation and nuclear migration are crucial events in cell g rowth and differentiation of many eukaryotes. Here we show that KIP3, the sixth and final kinesin-related gene in Saccharomyces cerevisiae, is required for migration of the nucleus to the bud site in preparatio n for mitosis. The position of the nucleus in the cell and the orienta tion of the mitotic spindle was examined by microscopy of fixed cells and by time-lapse microscopy of individual live cells. Mutations in KI P3 and in the dynein heavy chain gene defined two distinct phases of n uclear migration: a KIP3-dependent movement of the nucleus toward the incipient bud site and a dynein-dependent translocation of the nucleus through the bud neck during anaphase. Loss of KIP3 function disrupts the unidirectional movement of the nucleus toward the bud and mitotic spindle orientation, causing large oscillations in nuclear position. T he oscillatory motions sometimes brought the nucleus in close proximit y to the bud neck, possibly accounting for the viability of a kip3 nul l mutant. The kip3 null mutant exhibits normal translocation of the nu cleus through the neck and normal spindle pole separation kinetics dur ing anaphase. Simultaneous loss of KIP3 and kinesin-related KAR3 funct ion, or of KIP3 and dynein function, is lethal but does not block any additional detectable movement. This suggests that the lethality is du e to the combination of sequential and possibly overlapping defects. E pitope-tagged Kip3p localizes to astral and central spindle microtubul es and is also present throughout the cytoplasm and nucleus.