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Originally published in Science Express on 4 December 2008
Science 19 December 2008:
Vol. 322. no. 5909, pp. 1851 - 1854
DOI: 10.1126/science.1164096
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Reports

RNA Exosome Depletion Reveals Transcription Upstream of Active Human Promoters

Pascal Preker1, Jesper Nielsen2, Susanne Kammler1*, Søren Lykke-Andersen1, Marianne S. Christensen1, Christophe K. Mapendano1, Mikkel H. Schierup2 and Torben Heick Jensen1{dagger}

1 Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology, C. F. Møllers Alle, Building 1130, Aarhus University, Denmark.
2 Bioinformatics Research Center, C. F. Møllers Alle, Building 1110, Aarhus University, Denmark.


Figure 1 Fig. 1. PROMPTs are produced immediately upstream of annotated TSSs and are degraded by the RNA exosome. (A) Relative stabilization of RNA from hRrp40 knockdown over control cells, sorted according to annotated genomic features (http://genome.ucsc.edu/cgi-bin/hgTracks) and normalized to the total signal over the entire ENCODE region. (B) PROMPT signature of a 500-kb ENCODE region (ENr323), showing the log2 transformed hRrp40-siRNA/eGFP-siRNA signal ratio (blue track) below the location of annotated genes (red bars) with their orientation of transcription indicated by arrows. The bottom track shows hRrp40-siRNA/eGFP-siRNA signal peaks (see supporting online material). (C) RT-qPCR analysis of 10 representative PROMPT regions. HeLa cells were treated with eGFP siRNA (control) or the experimental samples hRrp40, hRrp6, hRrp44, or both hRrp6 and hRrp44, as indicated. Mean values with standard deviations from at least three experiments are shown as fold increase in RNA levels of experimental over control samples. All data were normalized to an internal control, glyceraldehyde phosphate dehydrogenase (GAPDH) mRNA. For numbering of PROMPTs, see table S4. [View Larger Version of this Image (21K GIF file)]
 

Figure 2 Fig. 2. PROMPT expression maps to 0.5 to 2.5 kb (i) upstream of TSSs, (ii) can occur in both orientations, and (iii) requires the gene promoter. (A) Composite RNA profiles upstream of all 1594 (top) or 64 low-complexity (bottom) TSSs. Raw (single-channel) data (smoothened over a 10-bp window) from hRrp40-siRNA treated cells, control (eGFP) siRNA–treated cells, and their ratio are shown as indicated. The left y axis denotes values for raw data, and the right y axis denotes the log2-transformed ratio of the raw data, scaled to center at zero. Positions in base pairs of RNA signals relative to TSSs are shown on the x axes. (B) The sense (blue)/antisense (red) directionality of selected PROMPTs was determined by RT-qPCR with gene-specific primers (~1 kb upstream the TSS) in either orientation in combination with a T20VN primer that hybridizes to the 3' poly(A) tail. Fold increases relative to the lowest value in control cells (set to 1) are plotted. PROMPTs are ordered such that the one with the highest preference for sense transcription is at the top. (C) Generation of promoter-upstream transcription in nonhuman DNA. Plasmids containing the β-globin gene under control of a viral promoter (CMV) or its {Delta}CMV control were transiently transfected into HeLa cells. Both constructs have an insertion of bacteriophage {lambda} DNA (red bar) upstream and a strong SV40 poly(A) site (black box) downstream of the β-globin gene. RNA levels were analyzed by RT-qPCR. Read-through transcription from the β-globin promoter was measured with the use of two amplicons upstream of the {lambda} DNA ("read through"). The "control" amplicon has no complementary sequence in the {Delta}CMV plasmid. Values on the y axis are percentages of GAPDH mRNA levels. The dashed box in the linear plasmid representation (top, not drawn to scale) encloses the region that is deleted in the {Delta}CMV construct. Mean values with standard deviations (n = 3) are shown. [View Larger Version of this Image (42K GIF file)]
 

Figure 3 Fig. 3. PROMPT regions are actively transcribed. (A) Details of transcript levels from this study compared with previously published ChIP-chip data for PROMPT and 5' regions of two representative genes. Genomic coordinates are shown on top in numbers of base pairs. (B) Composite profiles of RNA stabilization in the PROMPT regions of 64 low-complexity TSSs displayed as in Fig. 2A and compared with the indicated data sets. [View Larger Version of this Image (44K GIF file)]
 

Figure 4 Fig. 4. Overall correlation of PROMPT- and gene-expression levels. (Left) Scatter plot of RNAPII distribution as measured by ChIP-chip over all 1594 TSSs in the ENCODE region (data taken from GEO, accession number GSE6391). Data were integrated over 1.5 kb before (y axis, "PROMPT") and after (x axis, "Gene Start") each TSS and plotted against each other. The slope of the linear regression is 0.68 with a P value of ≤10–300 (t test, product-moment correlation) and an r2 value of 0.61 [degrees of freedom (df) = 1511]. (Right) Scatter plot of single-channel RNA microarray signals from hRrp40 siRNA-treated cells created as above with the exception that, in the gene, only data corresponding to exonic DNA were used to remove exon/intron biases (fig. S3). Statistical values are slope = 0.45, P value < 10–137, and r2 = 0.39 (df = 1420). [View Larger Version of this Image (29K GIF file)]
 

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