Novel potential mitotic motor protein encoded by the fission yeast cut7+ gene

Abstract

The structure equivalent to higher eukaryotic centrosomes in fission yeast, the nuclear membrane-bound spindle pole body, is inactive during interphase. On transition from G2 to M phase of the cell cycle, the spindle pole body duplicates; the daughter pole bodies seed microtubules which interdigitate to form a short spindle that elongates to span the nucleus at metaphase. We have identified two loci which, when mutated, block spindle formation. The predicted product of one of these genes, cut7+, contains an amino-terminal domain similar to the kinesin heavy chain head domain, indicating that the cut7+ product could be a spindle motor. The cut7+ gene resembles the Aspergillus nidulans putative spindle motor gene bimC, both in terms of its organization with a homologous amino-terminal head and no obvious heptad repeats and in the morphology of the mutant phenotype. But we find no similarity between the carboxy termini of these genes, suggested that either the cut7+ gene represents a new class of kinesin genes and that fission yeast may in addition contain a bimC homologue, or that the carboxy termini of these mitotic kinesins are not evolutionarily conserved and that the cut7+ gene belongs to a subgroup of bimC-related kinesins.

Contributions of Microtubule Dynamic Instability and Rotational Diffusion to Kinetochore Capture

“…Fission yeasts carrying the cut7-ts allele arrest in early mitosis at restrictive temperature (36-37 C), because bipolar spindles cannot form when cut7p is inactive (40). These cells instead form monopolar mitotic spindles, in which individual fluorescently labeled mitotic MTs can be imaged and tracked (Fig.…”

Two Related Kinesins,klp5+andklp6+, Foster Microtubule Disassembly and Are Required for Meiosis in Fission Yeast

“…klp5 ϩ and klp6 ϩ are the fifth and sixth motor proteins demonstrated to have a major role in fission yeast meiosis (cut7 ϩ , Hagan and Yanagida, 1990; dhc1 ϩ , Yamamoto et al, 1999; pkl1 ϩ and klp2 ϩ , Troxell et al, 2001), whereas only cut7 ϩ is essential for mitosis (Hagan and Yanagida, 1990). This indicates that fission yeast meiosis is very sensitive to the normal functioning of the microtubule cytoskeleton compared with vegetative growth.…”

“…The Schizosaccharomyces pombe genome encodes nine kinesin-related genes from seven subfamilies and one cytoplasmic dynein (Hagan and Yanagida, 1990;Pidoux et al, 1996;Yamamoto et al, 1999;Brazer et al, 2000;Browning et al, 2000;Troxell et al, 2001; pombe genome project). Among the kinesin subfamilies found in fission yeast, three have direct effects on microtubule dynamics and higher order microtubule organization (Goldstein and Philp, 1999).…”

cut11+: A Gene Required for Cell Cycle-dependent Spindle Pole Body Anchoring in the Nuclear Envelope and Bipolar Spindle Formation inSchizosaccharomyces pombe

“…This leads to an asymmetric separation of chromosomes, resulting in either aneuploidy or aploidy and cell death (Hirano et al, 1986;Samejima et al, 1993). Several cut mutants have been characterized; their gene products cover a broad range of functions, including components of the spindle pole body (Bridge et al, 1998) and the anaphase-promoting complex (Samejima and Yanagida, 1994a,b), enzymes involved in DNA topology (Hirano et al, 1986;Saka et al, 1994) and replication (Saka et al, 1994), and microtubule-dependent motors (Hagan and Yanagida, 1990). cut11 ϩ , on the other hand, appears to be an essential component of the mitotic spindle pole body as well as a component of the nuclear pore complex.…”