Interactions between the nod+ kinesin-like gene and extracentromeric sequences are required for transmission of a Drosophila minichromosome.

In this study, we demonstrate a role for extracentromeric sequences in chromosome inheritance. Genetic analyses indicate that transmission of the Drosophila minichromosome Dp1187 is sensitive to the dosage of nod+, a kinesin-like gene required for the meiotic transmission of achiasmate chromosomes. Minichromosome deletions displayed increased loss rates in females heterozygous for a loss-of-function allele of nod (nod/+). We have analyzed the structures of nod-sensitive deletions and conclude that multiple regions of Dp1187 interact genetically with nod+ to promote normal chromosome transmission. Most nod+ interactions are observed with regions that are not essential for centromere function. We propose that normal chromosome transmission requires forces generated outside the kinetochore, perhaps to maintain tension on kinetochore microtubules and stabilize the attachment of achiasmate chromosomes to the metaphase spindle.