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.

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The presynaptic phase of homologous recombination requires the formation of a filament of single-stranded DNA (ssDNA) coated with a recombinase enzyme. In bacteriophage T4, at least three proteins are required for the assembly of this presynaptic filament. In addition to the T4 recombinase, uvsX protein, the T4 ssDNA binding protein (gp32), and the uvsY recombination accessory protein are also required. Here we report on a detailed analysis of a tripartite filament containing ssDNA bound by stoichiometric quantities of both uvsY and gp32, which appears to be an important intermediate in the assembly of the T4 presynaptic filament. We demonstrate that uvsY and gp32 simultaneously co-occupy the ssDNA in a noncompetitive fashion. In addition, we show that protein-protein interactions between uvsY and gp32 are not required for the assembly of this ternary complex and do not affect the affinity of uvsY for the ssDNA lattice. Finally, we demonstrate that the interaction of gp32 with the ssDNA is destabilized within this complex, in a manner which is independent of gp32-uvsY interactions. The data suggest that the uvsY protein acts to remodel the gp32-ssDNA complex via uvsY-ssDNA interactions. The implications of these findings for the mechanism of presynapsis in the T4 recombination system are discussed.

The effect of ecdysteroid signaling on Drosophila female precopulatory behavior was investigated using two types of mutants with either globally reduced ecdysteroid availability or reduced expression of ecdysone receptors in fruitless neurons, known to control sexual behavior. While being courted by males, mutant females performed significantly less full ovipositor extrusion behavior to reject male copulation attempts. Ecdysteroid depleted females (ecdysoneless1) performed male-like courtship behaviors, including unilateral wing extension and song production with patterns very similar to male courtship song. These results support the hypothesis that ecdysteroids modulate female sexual behavior, perhaps acting as a regulator of sexual motivation, and as a component affecting the performance of sex specific behavior patterns.

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