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. 2000 Sep 1;14(17):2192–2205. doi: 10.1101/gad.176700

Figure 4.

Figure 4

Overexpression of wild-type PIM inhibits sister chromatid separation. prd–GAL4 (A–D) or da–GAL4 (E,F) was used for overexpression of wild-type PIM with carboxy-terminal myc epitopes from either one (A,B) or two (C–F) UAS–pim–myc transgene copies. Embryos were fixed either after mitosis 16 (A–D) or during mitosis 16 (E,F) and labeled with antibodies against the myc epitope (myc; A,C), tubulin (tub; E) and with a DNA stain (DNA; B,D,F). Overexpression from one UAS–pim–myc copy does not affect progression through the sixteenth embryonic division. The normal nuclear density is therefore observed in the prd–GAL4-expressing segments (A,B, white horizontal bars). In contrast, overexpression from two UAS–pim–myc copies results in inhibition of sister chromatid separation during mitosis 16. Arrowheads in E and F indicate cells during telophase of mitosis 16 with unseparated chromosomes. As a consequence, cytokinesis fails as well, but exit from mitosis 16 occurs normally. This failure of sister chromatid separation and cytokinesis is evidenced by the lower density of interphase nuclei in the prd–GAL4-expressing segments (C,D, white bars) after mitosis 16.