Fig. 3.

Top3β and RISC mutants are similar in disrupting heterochromatic gene silencing by PEV assay. a A cartoon illustrates the PEV assay using white gene as reporters. See Results for description. The heterochromatin is marked by gray area, whereas HP1 is marked by green balls. HMT denotes histone methyltransferase. b Representative eye images show that Top3β is a suppressor of PEV similarly as are RISC components (AGO2 and p68/Rm62), and Su(var)3-9. Increased red color indicates suppression of silencing of white gene. Three white gene reporter lines were indicated on the left, with letters in parentheses indicating the chromosome with the reporter. Different mutant background is indicated on top. w¹¹¹⁸ serves as a negative control as Top3β²⁶ was generated in its background. c A LacZ reporter-based PEV assay shows that Top3β mutant suppresses PEV similarly as does Su(var)3-9 mutant. PEV suppression is indicated by increased blue color due to de-silencing of the LacZ. Su(var)3-9^06/+ served as a positive control, whereas w¹¹¹⁸ as a negative control, as indicated on top. d Schematic representation summarizing the PEV modifications by Top3β mutants for reporters located on different chromosomes. Note that Top3β enhanced PEV for reporters in heterochromatin of chromosome 4, which is known to be different from those on heterochromatin⁶²