dPNUTS is a nuclear protein that colocalises with transcriptionally active RNAPII on salivary gland polytene chromosomes.

A) Distribution of dPNUTS transcripts detected by RNA in situ hybridization; dPNUTS transcripts are maternally provided (top left) and are ubiquitously distributed in embryos at cellularisation (top right). At gastrulation, dPNUTS mRNA levels are enriched in the germband and in the fore- and hind-gut (fg and hg, respectively). Later, dPNUTS is highly expressed in the brain (br) and ventral nerve cord (vnc). Embryonic stage and approximate age, hours post fertilization (hpf), are indicated. B) 3rd instar wing discs stained to reveal the distribution of ectopically expressed Myc-tagged dPNUTS (green in merge), Histone H3S10ph (red in merge, marking mitotic nuclei) and DNA. C) Images of whole mount salivary gland and magnified images of an individual nucleus (below), stained to show the localization of Myc-tagged dPNUTS (green in merge) and DNA (magenta in merge). D) Line scans of images in C) reveal that Myc-tagged dPNUTS is localised to interbands that stain weakly for DNA. Fluorescence intensity of anti-Myc antibody and TOPRO-3 staining was measured along a line through the indicated chromosomal region in the images shown. The profile plot below shows that the peaks of Myc-PNUTS and DNA of staining do not overlap. E) Polytene chromosomes from salivary gland squashes showing that dPNUTS localises to a number of discrete bands that are broadly distributed. F) Merging of the green signal representing dPNUTS with the red signal representing RNAPII Ser2-P (H5) identifies sites where these two proteins co-localize (example indicated with arrow). The relative signals of dPNUTS and RNAPII Ser2-P vary between sites, but the majority dPNUTS loci colocalize with RNAPII Ser2-P staining (star indicates example where only dPNUTS staining is visible).