YY1 plays a critical role in Xist localization by bridging Xist RNA and chromatin. The image shows that Xist cloud (green) formation is dependent on the presence/absence of YY1 (red) in female cells. This image is the original nucleus. This image relates to a paper that appeared in the Dec. 14, 2012, issue of Science, published by AAAS. The paper, by Jeannie T. Lee at Howard Hughes Medical Institute in Boston, MA was titled, "Epigenetic Regulation by Long Noncoding RNAs."