Fig. 7. Sumoylation controls proliferation of progenitor cells along with Dacapo.

Hematopoietic progenitors express high level of either one or both, ZCL2897 (green) and Dome>GFP (red). Some of these cells and cells in transition zone express 76B-Gal4 (cyan). At third instar stage, progenitors enter quiescence. Heterogeneity and absence of mature marker expression suggest similarity to mammalian transit amplifying cells (Morrison and Spradling, 2008; Shaker and Rubin, 2010) or Drosophila testis progenitors (Shivdasani and Ingham, 2003). We propose that sumoylation regulates multiple events including maintenance of high levels of Dacapo protein in these cells. In the absence of sumoylation enzymes Aos1/Uba2, Ubc9, and PIAS, these cells fail to quiesce and progress into G2/M phase (cells with purple outline) and misdifferentiate (dark green cells); dysplasia and tumorogenesis follow.