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. Author manuscript; available in PMC: 2012 Jun 8.
Published in final edited form as: Cold Spring Harb Symp Quant Biol. 2011 Apr 5;75:453–460. doi: 10.1101/sqb.2010.75.050

Figure 5. Transcription on a condensed template.

Figure 5

(A–C) Tethering of the VP17 acidic activator using a EGFP-lac repressor-VP16 fusion protein (red) to a heterochromatic amplified chromosome region results in extensive decondensation and extended large-scale chromatin fibers. BrUTP pulse labeling (green) shows large amounts of nascent transcripts surrounding these large-scale chromatin fibers. (D) DHFR multi-copy BAC transgenes assemble into a compact large-scale chromatin fiber despite transcriptional activity within 2–3 fold of the endogenous DHFR gene. Fluorescence in situ hybridization using the entire BAC as a probe (green) versus probes covering the 34 kb DHFR gene (red) reveal the absence of any detectable looping of the DHFR genes outside of these large-scale chromatin fibers. DAPI staining is grey.