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First published online August 9, 2007
doi: 10.1242/10.1242/jcs.007633

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Transcriptional interference: an unexpected layer of complexity in gene regulation

¹ Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
² Molecular Epigenetics Group, Life Sciences Institute, Department of Zoology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada

View larger version (38K): [in this window] [in a new window]   Fig. 1. Mechanisms of TI. (A) Tandem and convergent orientation of genes that permit sense and antisense TI. (B) Transcription of the untranslated RNA through the promoter could prevent recruitment of Pol II (shown with an unphosphorylated C-terminal domain in red), general transcription factors (GTFs) or specific transcription factors (TF) to the target. The transcribing Pol II from the ncRNA promoter is show in green and with a phosphorylated C-terminal domain. (C) Transcription of ncRNA could prevent promoter clearance or elongation. (D) Transcription of ncRNA could cause premature termination, shown here as resulting from a collision between converging polymerases that dislodges the Pol II transcribing the target gene.

View larger version (18K): [in this window] [in a new window]   Fig. 2. Schematic diagram showing mechanism of TI at the IME4 locus in yeast. The IME4 locus is transcribed by a sense and an antisense transcript in haploid cells of the a or mating type because the MATa- repressor that represses the antisense transcript is not present. As a result, IME4 protein is not produced. In diploid MATa/ cells, MATa- represses transcription of the IME4 antisense transcript. This allows production of IME4 and the initiation of meiosis.

View larger version (25K): [in this window] [in a new window]   Fig. 3. The BX-C and untranslated RNAs. (A) Relationship between embryonic parasegments, cis-regulatory domains of the BX-C, and expression domains of Hox genes in embryos. The names of the regulatory regions are given above, and the embryonic expression domains of Hox genes are shown below. Regulatory domains set the anterior borders of the parasegments indicated but also function in posterior parasegments. (B) Molecular map of BX-C. Cis-regulatory domains are colored as in A, and Hox mRNA structure is shown (simplified for Abd-B) below. Regulatory domains marked in red are transcribed to give untranslated RNAs. (C) Detailed map of untranslated RNAs of the bxd regulatory region [after Lipshitz et al. (Lipshitz et al., 1987)]. Grey bars show additional transcripts identified recently (Sanchez-Elsner et al., 2006). The locations of the maintenance element (ME) and the transcription start site for Ubx are indicated. The bottom panel shows that Ubx (green) and bxd ncRNA (red) are expressed in different cells of the blastoderm embryo [adapted from Petruk et al. (Petruk et al., 2006)].