The BTB domain is necessary but not sufficient for association with the Su(Hw) complex. (A) Distribution of myc-CP190dBTB and Cp190 on polytene chromosomes. The polytene chromosomes of the y2(upper panel) and of the y2; P[Ubi63e::myc-CP190dBTB]; CP190P1/CP1903(lower panel) flies were stained with anti-CP190 (left column) and anti-Mod(mdg4)67.2 (middle column). Shown are the tips of X chromosomes with the y locus (white arrows) and a band nears y (yellow arrows). (B) Co-immunoprecipitation of Cp190 and Mod(mdg4)67.2. Immunonblots of anti-Cp190 (top panel) and anti-Mod(mdg4)67.2 (bottom panel). Proteins were immunoprecipitated with anti-Myc from y2ct6; P[Ubi63e::myc-CP190dBTB]/+; CP1903/TM6B pupae (lanes 1 and 2), with anti-Cp190 from y2ct6pupae (lanes 3 and 4), and with anti-Myc (lane 5) or pre-immune (lane 6) from y2ct6pupae. Input controls from myc-CP190dBTB (lane 7) and from y2ct6(lane 8) pupae. (C-D) Anti-Cp190 ChIP of known Su(Hw), CTCF, and BEAF32 loci assayed by Real-Time PCR (percentage of input DNA, n≥3), from y2ct6flies (C) and from ct6; P[Ubi63e::myc-CP190dBTB; CP1903/CP190P1flies (D). The 1A6 region is the negative control . All results were normalized to Fab-8. (E) Distribution of the mRFP-CP190 (red, left column), GFP-CP190dBTB (green, middle column) in a living salivary gland cell nucleus from a 3rd instar larva. An extra-chromosomal space containing GFP-CP190dBTB signals but not mRFP-CP190 signals (yellow arrows). The closer views (bottom row) are crops indicated by the white squares in the upper row. The white arrows point to two bands containing both mRFP-CP190 and GFP-CP190dBTB. (F) Distribution of GFP-CP190BTB-nls (green, left) and mRFP-CP190 (red) in the cell nucleus of a living salivary gland from a 3rd instar larva. The white arrows point an extra-chromosomal space containing GFP-CP190BTB-nls but not mRFP-CP190. The yellow arrows point to two mRFP-CP190 bands on polytene chromosomes that did not have detectable GFP-CP190BTB-nls signals.