Fig. 4.

a Binding of Umbrea depends on HP1 but not on Hip. Polytene chromosomes are stained with anti-Umbrea antibody and counterstained with Hoechst. Umbrea binding is strongly reduced in Su(var)2-5-deficient larvae. In these larvae almost no HP1 staining could be detected (not shown). In hip⁴¹ homozygous larvae virtually no Hip protein could be detected (shown in Schwendemann et al. 2008). In these larvae the binding of Umbrea appears unaffected along the arms of the chromosomes but is reduced at the chromocentre; b On chromosomes, chromatin-associated Umbrea is significantly reduced after salivary gland-specific RNAi depletion of Umbrea. The umbrea RNAi line 13072 under the control of UAS and the salivary gland specific driver line G61-Gal4 were used. Polytene chromosomes from umbrea RNAi mutants are stained with anti-Umbrea antibody (red) and counterstained with the DNA dye Hoechst 33258 (green); c Umbrea protein levels are reduced after Umbrea RNAi knock-down. Immunoblots of salivary gland protein extracts of control and salivary gland umbrea RNAi animals were probed with anti-Umbrea antiserum. As a loading control, we used anti-β-actin-antibody (abcam). In RNAi mutants Umbrea protein levels are dramatically reduced