Identification and characterization of the minimal <i>UBC9</i> promoter.

<p>(<b>A</b>) MCF-7 cells cultured in phenol red-free medium in the presence (black bars) or absence (white bars) of E₂ were transfected with the indicated constructs and assayed for luciferase activity after 48 hours. The numbers given for each construct indicate the 5’ and 3’ ends of the <i>UBC9</i> 5’-flanking region; the position numbered +1 corresponds to the transcription initiation site. Luciferase activity was expressed as fold change relative to that obtained from promoter-less vector <i>pGL</i>-basic, which was arbitrarily set to 1. Values were normalized for transfection efficiency by co-transfection with the <i>Renilla</i> expression plasmid and were given as mean ±SD obtained in four separate experiments. **P<0.01 (Student’s <i>t</i>-test). (<b>B</b>) <i>UBC9</i> sequence and putative transcription factor binding sites of the minimal <i>UBC9</i> promoter. Position +1 refers to the transcription initiation site. Putative transcription factor-binding sites predicted by the webtool PromoterSweep [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075695#B30" target="_blank">30</a>], including an imperfect ERE, a CCAAT box and an inverted CCAAT box (iCCAAT) are overlined.