dPNUTS binds to and co-localises with PP1 on chromosomes.

A) Predicted domain structure of dPNUTS and dPNUTS-S proteins, indicating the position of the putative PP1-binding motif (residues 722–726), which is located in the shortest yeast two-hybrid interacting clone (SIC) of dPNUTS. B) Beta-galactosidase assays showing binding of dPNUTS but not dPNUTS-S to all four D. melanogaster PP1 isoforms in the yeast two-hybrid system. C) dPNUTSWT, but not dPNUTSW726A, co-precipitates PP1 from nuclear extracts from adult flies. da-GAL4 UAS-HM-dPNUTSWT and da-GAL4 UAS-HM-dPNUTSW726A fly extracts were subjected to immunoprecipitation (IP) with Myc antibodies followed by immunoblotting with PP1 antibodies. Blots of total lysates confirmed levels of HM-tagged dPNUTS and PP1. D) dPNUTS and PP1 colocalise at many sites on polytene chromosomes. Inset is an enlarged view of the end of the X chromosome where this is clearly visible. Plot of fluorescence intensity of anti-PP1 and dPNUTS antibody staining, measured along a line through the indicated chromosomal region, reveal the degree of colocalisation between PP1 and dPNUTS.