Cell Cycle

Coordinating Mitosis and Morphogenesis

Science's STKE  06 Jun 2000:
Vol. 2000, Issue 35, pp. tw9
DOI: 10.1126/stke.2000.35.tw9

Two groups have identified the gene for tribbles in Drosophila, whose product acts to inhibit the activity of the Drosophila homolog of the CDC25 phosphatase, String. String activity allows the phase transition from G2 to M in the cell cycle. Großhans and Wieschaus identified tribbles in a genetic screen for mutants in which the embryonic cells in the ventral region have accelerated entry into mitosis and, thus, do not properly form the ventral furrow. Mata et al. identified tribbles in a genetic screen for mutants that have increased number of cells (cystocytes) in the ovary. Mata et al. demonstrated that Tribbles promotes the proteasome-mediated degradation of String, thereby delaying mitosis. Both groups show that overexpression of tribble inhibits mitosis. Tribbles shows homology to serine-threonine kinases; however, conserved residues in the catalytic domain and ATP-binding domain are missing. Furthermore, Großhans and Wieschaus mutated a critical lysine in the predicted catalytic center of Tribbles and found this mutant of Tribbles was able to delay the cell cycle when injected into embryos, suggesting that Tribbles is not functioning as a kinase. During embryogenesis, it is essential for cells to coordinate between mitotic programs and morphogenic programs. Tribbles is one component in the pathway controlling the switch between these two programs.

Großhans, J., and Wieschaus, E. (2000) A genetic link between morphogenesis and cell division during formation of the ventral furrow in Drosophila. Cell 101: 523-531. [Online Journal]

Mata, J., Curado, S., Ephrussi, A., and Rørth, P. (2000) Tribbles coordinates mitosis and morphogenesis in Drosophila by regulating String/CDC25 proteolysis. Cell 101: 511-522. [Online Journal]