pkl1⁺andklp2⁺: Two Kinesins of the Kar3 Subfamily in Fission Yeast Perform Different Functions in Both Mitosis and Meiosis

Abstract

We have identified Klp2p, a new kinesin-like protein (KLP) of the KAR3 subfamily in fission yeast. The motor domain of this protein is 61% identical and 71% similar to Pkl1p, another fission yeast KAR3 protein, yet the two enzymes are different in behavior and function. Pkl1p is nuclear throughout the cell cycle, whereas Klp2p is cytoplasmic during interphase. During mitosis Klp2p enters the nucleus where it forms about six chromatin-associated dots. In metaphase-arrested cells these migrate back and forth across the nucleus. During early anaphase they segregate with the chromosomes into two sets of about three, fade, and are replaced by other dots that form on the spindle interzone. Neither klp2 ϩ nor pkl1 ϩ is essential, and the double deletion is also wild type for both vegetative and sexual reproduction. Each deletion rescues different alleles of cut7 ts , a KLP that contributes to spindle formation and elongation. When either or both deletions are combined with a dynein deletion, vegetative growth is normal, but sexual reproduction fails: klp2⌬,dhc1-d1 in karyogamy, pkl1⌬,dhc1-d1 in multiple phases of meiosis, and the triple deletion in both. Deletion of Klp2p elongates a metaphase-arrested spindle, but pkl1⌬ shortens it. The anaphase spindle of klp2⌬ becomes longer than the cell, leading it to curl around the cell's ends. Apparently, Klp2p promotes spindle disassembly and contributes to the behavior of mitotic chromosomes.

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

“…pombe has two KAR3 homologs, pkl1 ϩ and klp2 ϩ (Pidoux et al, 1996;Troxell et al, 2001). Neither of these kinesins is essential, either individually or together, but null mutants have altered sensitivities to TBZ and severe meiotic phenotypes.…”

“…Kinesins (Meluh and Rose, 1990) and dynein (Yamamoto et al, 1999;Troxell et al, 2001) are important for meiosis in Figure 7. Klp5p and Klp6p localize to cytoplasmic microtubules in interphase and spindles in mitosis.…”

“…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).…”

“…S. pombe expresses two members of the KAR3 subfamily, pkl1 ϩ and klp2 ϩ . These promote microtubule disassembly and, together with dynein, are essential for meiosis (Troxell et al, 2001). S. pombe also expresses tea2 ϩ , a member of the KIP2 subfamily, which promotes microtubule growth (Cottingham and Hoyt, 1997).…”