CENP-meta, an Essential Kinetochore Kinesin Required for the Maintenance of Metaphase Chromosome Alignment in Drosophila

Abstract

CENP-meta has been identified as an essential, kinesin-like motor protein in Drosophila. The 257-kD CENP-meta protein is most similar to the vertebrate kinetochore-associated kinesin-like protein CENP-E, and like CENP-E, is shown to be a component of centromeric/kinetochore regions of Drosophila chromosomes. However, unlike CENP-E, which leaves the centromere/kinetochore region at the end of anaphase A, the CENP-meta protein remains associated with the centromeric/kinetochore region of the chromosome during all stages of the Drosophila cell cycle. P-element–mediated disruption of the CENP-meta gene leads to late larval/pupal stage lethality with incomplete chromosome alignment at metaphase. Complete removal of CENP-meta from the female germline leads to lethality in early embryos resulting from defects in metaphase chromosome alignment. Real-time imaging of these mutants with GFP-labeled chromosomes demonstrates that CENP-meta is required for the maintenance of chromosomes at the metaphase plate, demonstrating that the functions required to establish and maintain chromosome congression have distinguishable requirements.

CENP-E Is Essential for Reliable Bioriented Spindle Attachment, but Chromosome Alignment Can Be Achieved via Redundant Mechanisms in Mammalian Cells

“…A different set of windowed frames in Figure 7c shows a chromosome (arrow) undergoing normal congression to the spindle equator with a brief reversal of motion similar to that previously reported in newt lung (Skibbens et al, 1993) and PtK (Khodjakov and Rieder, 1996) cells. Congressed chromosomes at the metaphase plate and many of the monooriented chromosomes showed vigorous oscillations, but in contrast to what was reported for Drosophila (Yucel et al, 2000), we did not detect aligned chromosomes leaving the metaphase plate. Some of the monooriented chromosomes on the astral side of the pole did not appear to oscillate (see video).…”

“…Therefore, a reduction in kMt binding in Drosophila due to the absence of CENP-meta, coupled with the normal stochastic variation in time, could easily result in some kinetochores losing all of their Mts and migrating to the attached spindle pole. In support of this hypothesis, sister chromatids of most unaligned chromosomes in mutant cells do not separate and segregate to opposite spindle poles at the onset of anaphase, indicating that one sister kinetochore was unbound (Yucel et al, 2000; note, the checkpoint is turned off in Drosophila embryos). Chromosomes that did segregate to opposite poles could have achieved bioriented attachment at, or just after, the start of anaphase because Drosophila kinetochores depleted of CENP-meta appear to achieve bioriented attachment more readily than do mammalian kinetochores depleted of CENP-E.…”

“…Nevertheless, some chromosomes fall off the metaphase plate to resume a monopolar orientation (Yucel et al, 2000). We do not observe this instability of metaphase alignment in anti-CENP-E-injected CF-PAC cells, even though congressed chromosomes oscillate vigorously (video supplement 1).…”

“…Two CENP-E homologs have been discovered in Drosophila (Yucel et al, 2000). Live cell imaging demonstrated that P-element disruption or complete removal of one of the CENP-E homologs, CENP-meta, results in chromosomes that undergo congression but frequently fail to maintain a stable alignment at the metaphase plate.…”

Mitosis-specific kinesins in Arabidopsis

“…Chromosomes are aligned by numerous kinesins in animal cells. Kinesin-4 members, such as Drosophila DmKLP3A or human and Xenopus KID, act on the chromosomal arms, whereas Kinesin-7 members (DmCENPmeta and HsCENP-E) and Kinesin-13 members (HsMCAK) function at the centromere [55][56][57]60,82]. (c) During anaphase A, chromosomes are separated to the spindle poles.…”