Kinesins are intracellular transport motors found in all eukaryotes. Here we describe a special subgroup of kinesin like proteins in C. elegans that are distinguished by location of their motor domain in the carboxyl terminal of the protein. First such atypical C-terminal motor in C. elegans , CeKLP-3 was identified by sequencing a rare cDNA clone (Khan et al., 1997). CeKLP3, encoded by the
klp-3 gene (Cosmid T09A5.2) is located on LGII, as one of the C-terminus kinesins, and belongs to the yeast Kar3 (Meluh and Rose, 1990) and Drosophila ncd kinesins (Endow et al., 1990), that are retrograde motors, mediate chromosmal movement during mitotic cell divisions. In a PCR amplification based screening assay, using degenerate primers to the conserved ATP and MT binding sites in the motor domain as probes, we have identified three new cDNA clones that reveal new C-terminus kinesins in C. elegans ( KLP-15, KLP-16, and KLP-17). Northern blot analysis suggest that these cDNA clones are close to full length, deduced from genomic sequences. Phylogenetic relationship of these motor proteins suggests that KLP-15, KLP-16, and KLP-17, are members of the ncd/kar3 subfamily, primarily involved in chromosome segregation. However secondary structure of these new members is different in the non-motor domain, i.e. the stalk and amino terminus cargo binding domains have different size and charge distribution. The CeKLP-3, is involved in chromosome separation, as the overexpression of the
klp-3 in transgenic animals increases the incidence of males caused by nondisjunction of the X-chromosome, and results in polyploid embryos that are arrested in early development. Similarly, an anti-sense construct of the
klp-3 cDNA expressed under the heat shock promoter affects chromosomal segregation (Khan et al.,1997). Our data on embryonic insitu hybridization suggest that
klp-15 and
klp-16 express at a high level in early embryogenesis in the cytoplasm, but the
klp-17 expresses strongly in the cell nuclei. We are in the process to identify the role of of all three genes using dsRNAi and the promoter fusion expression using gfp . We thank A. Coulson, A. Fire, Yuji Kohara, Y. Ohshima , T. Stiernagle for materials, and Monbusho for a research grant to SSS.