Transcriptional states of en. Fly lines with 3XFLAG-tagged Pho, dRing/Sce, Esc, and Scm were generated. These proteins were chosen because they are present in different PcG protein complexes and might preferentially bind in the “OFF” versus the “ON” transcriptional state. All proteins were first tagged at the C-terminus. C-terminally tagged Scm-FLAG acted in a dominant negative fashion when ubiquitously expressed in a wild-type background, as indicated by strong PcG-type transformations (data not shown). Therefore, we generated and proceeded with an N-terminally tagged FLAGScm protein, which did not produce a phenotype when expressed ubiquitously in a wild type background. UAS-Pho-FLAG was crossed with en-GAL4 or ci-GAL4, and FLAG-expression was examined in whole embryos and imaginal discs from wandering 3rd instar larvae. As expected, Pho-FLAG driven by en-GAL4 was expressed in embryos (not shown) and in discs in a pattern that almost completely overlapped with endogenous en (Fig. 2A ). Pho-FLAG driven by ci-GAL4 was expressed in a non-overlapping pattern complementary to endogenous en (Fig. 2D ), consistent with the reported expressionResults 25331948 Analysis of ncRNAs in the en-inv regioninv and en comprise a 115 kb domain flanked by the 39 end of the genes E(Pc) and tou (Fig. 1). We conducted in situ RNA hybridization on whole embryos, using DIG-labeled RNA probes designed to recognize RNAs transcribed in either direction throughout the entire 115 kilobase domain (Fig. 1). Positive control probes were made against the en and inv transcripts, and against a nc RNA Pluripotin encoding a micro-RNA arising from the iab-8 region in the BX-C. This probe yielded a robust signal in the A8 region (Fig. 1), as described previously [30]. No specific signal was Homotaurine web detected within the interval between the 39 end of E(Pc) and the 59 end of inv region, which contains two inv PREs (Figure 1B, panels 1?). In the inv-en intergenic region, a specific signal resembling the inv expression pattern (Fig. 1A) was obtained using a probe just downstream of the inv transcript (Fig. 1B, panel 5). We suspect that this signal could be the result of transcriptional read through. In the next fragment, a transient pair-rule expression pattern was detected using a probe from the other strand (Fig. 1B, panel 6). Moving to the region upstream of the en transcription unit, no specific signal was observed with probes designed to detect transcription from the en PRE (Fig. 1B, panels 7 and 8). This result differs from what was reported by Schmitt et al. [20], who detected a weak stripe signal in germ band elongated embryos with a probe to the en PRE. We were also unable to detect this weak stripe signal using the exact probes used in their experiments (data notPcG Proteins Bind Constitutively to the en GeneFigure 1. Whole mount embryo in situ hybridization reveals that ncRNAs are not detectable at the known en and inv PREs. Grey Line indicates genomic DNA, with the coordinates listed at both ends (genome version R5.1). DIG-labeled RNA probes were generated to cover the entire region shown, on both strands. (A) Positive controls showing robust signal from en and inv probes, and from a probe against miR-iab-8, a miRNA in the BX-C [30]. (B) Selected in situ results from inv-en region. Panels 1? and 7, 8 show non-specific background staining using probes to detect RNAs transcribed in the regions of the inv and en PREs. Several probes yielded specific signals. Panels 5 and 9 show an en-like patt.Transcriptional states of en. Fly lines with 3XFLAG-tagged Pho, dRing/Sce, Esc, and Scm were generated. These proteins were chosen because they are present in different PcG protein complexes and might preferentially bind in the “OFF” versus the “ON” transcriptional state. All proteins were first tagged at the C-terminus. C-terminally tagged Scm-FLAG acted in a dominant negative fashion when ubiquitously expressed in a wild-type background, as indicated by strong PcG-type transformations (data not shown). Therefore, we generated and proceeded with an N-terminally tagged FLAGScm protein, which did not produce a phenotype when expressed ubiquitously in a wild type background. UAS-Pho-FLAG was crossed with en-GAL4 or ci-GAL4, and FLAG-expression was examined in whole embryos and imaginal discs from wandering 3rd instar larvae. As expected, Pho-FLAG driven by en-GAL4 was expressed in embryos (not shown) and in discs in a pattern that almost completely overlapped with endogenous en (Fig. 2A ). Pho-FLAG driven by ci-GAL4 was expressed in a non-overlapping pattern complementary to endogenous en (Fig. 2D ), consistent with the reported expressionResults 25331948 Analysis of ncRNAs in the en-inv regioninv and en comprise a 115 kb domain flanked by the 39 end of the genes E(Pc) and tou (Fig. 1). We conducted in situ RNA hybridization on whole embryos, using DIG-labeled RNA probes designed to recognize RNAs transcribed in either direction throughout the entire 115 kilobase domain (Fig. 1). Positive control probes were made against the en and inv transcripts, and against a nc RNA encoding a micro-RNA arising from the iab-8 region in the BX-C. This probe yielded a robust signal in the A8 region (Fig. 1), as described previously [30]. No specific signal was detected within the interval between the 39 end of E(Pc) and the 59 end of inv region, which contains two inv PREs (Figure 1B, panels 1?). In the inv-en intergenic region, a specific signal resembling the inv expression pattern (Fig. 1A) was obtained using a probe just downstream of the inv transcript (Fig. 1B, panel 5). We suspect that this signal could be the result of transcriptional read through. In the next fragment, a transient pair-rule expression pattern was detected using a probe from the other strand (Fig. 1B, panel 6). Moving to the region upstream of the en transcription unit, no specific signal was observed with probes designed to detect transcription from the en PRE (Fig. 1B, panels 7 and 8). This result differs from what was reported by Schmitt et al. [20], who detected a weak stripe signal in germ band elongated embryos with a probe to the en PRE. We were also unable to detect this weak stripe signal using the exact probes used in their experiments (data notPcG Proteins Bind Constitutively to the en GeneFigure 1. Whole mount embryo in situ hybridization reveals that ncRNAs are not detectable at the known en and inv PREs. Grey Line indicates genomic DNA, with the coordinates listed at both ends (genome version R5.1). DIG-labeled RNA probes were generated to cover the entire region shown, on both strands. (A) Positive controls showing robust signal from en and inv probes, and from a probe against miR-iab-8, a miRNA in the BX-C [30]. (B) Selected in situ results from inv-en region. Panels 1? and 7, 8 show non-specific background staining using probes to detect RNAs transcribed in the regions of the inv and en PREs. Several probes yielded specific signals. Panels 5 and 9 show an en-like patt.