Expression of homozygous CycB3Δ at the permissive temperature prevents or severely delays cell cycle progression at late anaphase.
When CycB3Δ is induced during the G2 phase of cycle 14, cytokinesis does progress albeit slowly to completion and initiation is delayed.
Heatshock expression of CycB3Δ produces embryos with arrested cells with condensed chromosomes at the poles. Cells proceed through the metaphase/anaphase transition with normal timing and separate their chromosomes with kinetics similar to wild-type, but then arrest with condensed chromosomes at the poles. This remains stable for at least 20 minutes in most cases. The separation of the spindle poles during anaphase B occurs as normal, however the organisation of the midbody is abnormal. Cells either lack the compacted foci of tubulin of the normal midbody, or showed foci lacking normal symmetry and organisation. Sometimes a more dynamic arrest is seen in which individual chromosomes leave the spindle pole and travel back along the spindle at rates comparable to anaphase rates. Occasionally, these chromosomes reach the opposite pole. Often, in cells where this phenomenon occurs, the spindle rotates in the plane of the epithelium. Cytogenetic furrow formation appears to proceed normally.
Expression causes a mitotic block in late anaphase (after sister chromosome separation).