pkl1(+) and klp2(+): Two kinesins of the Kar3 subfamily in fission yeast perform different functions in both mitosis and meiosis

We have identified Klp2p, a new kinesin-like protein (KLP) of the KAR3 subf amily in fission yeast. The motor domain of this protein is 61% identical a nd 71% similar to Pkl1p, another fission yeast KAR3 protein, yet the two en zymes are different in behavior and function. Pkl1p is nuclear throughout t he cell cycle, whereas Klp2p is cytoplasmic during interphase. During mitos is Klp2p enters the nucleus where it forms about six chromatin-associated d ots. In metaphase-arrested cells these migrate back and forth across the nu cleus. During early anaphase they segregate with the chromosomes into two s ets of about three, fade, and are replaced by other dots that form on the s pindle interzone. Neither klp2(+) nor pkl1(+) is essential, and the double deletion is also wild type for both vegetative and sexual reproduction. Eac h deletion rescues different alleles of cut7(ts), a KLP that contributes to spindle formation and elongation. When either or both deletions are combin ed with a dynein deletion, vegetative growth is normal, but sexual reproduc tion fails: klp2 Delta ,dhc1-d1 in karyogamy, pkl1 Delta ,dhc1-d1 in multip le phases of meiosis, and the triple deletion in both. Deletion of Klp2p el ongates a metaphase-arrested spindle, but pkl1 Delta shortens it. The anaph ase spindle of klp2 Delta 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.