Fig. 3. Localization of SCF along the dosage-compensated male X chromosome. (A-E) Extra SCF signals are associated with the male X chromosome when compared with autosomes or the female X chromosomes. Polytene chromosomes prepared from males (A-C) or females (D,E) were stained with antibodies or DAPI as indicated. Arrowheads indicate examples of the intensely stained SCF bands, which are identical in males and females. Note that the `milky way'-like signals between the intense bands are specific to the male X chromosome. (F-I) Most of the faint signals (but not the intense bands) of SCF colocalize with the MSL complex. Boxed regions in B and C are enlarged in F and G, and merged and split images are shown in H and I, respectively. (J-M) MSL-1 localization (J,K) and acetylation of histone H4K16 (L,M) along the male X chromosome are not affected by knockdown of SCF (J,L). To generate control individuals (carrying only GAL4) or RNAi-induced individuals (carrying both GAL4 and UAS-IRscf), the Act5C-GAL4 driver was crossed to yw or yw; [UAS-IRscf] (line 2-1) at 25°C. Polytene chromosomes from RNAi (J,L) or control (K,M) third-instar larvae were stained with DAPI (green in J,K) and anti-MSL-1 antibody (magenta in J,K), or with anti-acetylated H4K16 antibody (L,M). (N,O) The presence of SCF on the male X chromosome is reduced in a mof¹ mutant background. Polytene chromosomes were labeled with DAPI (green in N) and anti-SCF antibody (O; magenta in N). The tip of the X chromosome is marked by an arrow, and the X chromosome is boxed.