A kinesin-like protein required for distributive chromosome segregation in Drosophila.

The nod gene is required for the distributive segregation of nonexchange chromosomes during meiosis in D. melanogaster. Loss-of-function nod mutations cause nondisjunction and loss of nonrecombinant chromosomes both at meiosis I and during subsequent mitotic divisions. We have cloned the nod locus, examined its expression patterns, and determined its coding sequence. In adults the nod transcript is only present in females, consistent with the observation that males do not use the distributive segregation system. However, the nod locus is also transcribed in the embryonic, larval, and pupal stages of development, and possibly in all dividing cells. Finally, the N-terminal domain of the predicted nod protein has amino acid similarity to the mechanochemical domain of kinesin heavy chain; however, the C-terminal domain is unlike that of kinesin heavy chain or of any previously reported protein. Thus, the nod protein is a member of the kinesin superfamily and may be a microtubule motor.