DNA is decorated more beautifully than a Christmas tree, but the decorations are not just for looks—they serve the important function of regulating which genes get expressed, and when. Today’s image is from a paper describing the role of a protein that affects gene expression by regulating the accessibility of some regions of the DNA.
Chromatin is the packaged DNA and associated proteins found in the nucleus. Certain regions of chromatin are packaged or modified to make the underlying genes more or less accessible to the transcription machinery that results in gene expression. A recent paper describes the identification of UpSET, a fruit fly protein that binds to promoter regions of transcriptionally active genes. The upSET gene resembles the mammalian gene MLL5, which is found in a region frequently deleted in a subset of leukemias. In the absence of UpSET, according to Rincon-Arano and colleagues, cells have increased chromatin accessibility and express genes that normally flank the regions of UpSET binding. In the images above, fruit fly polytene chromosomes (blue) show staining for UpSET (green) in gene-rich regions.
Rincon-Arano, H., Halow, J., Delrow, J., Parkhurst, S., & Groudine, M. (2012). UpSET Recruits HDAC Complexes and Restricts Chromatin Accessibility and Acetylation at Promoter Regions Cell, 151 (6), 1214-1228 DOI: 10.1016/j.cell.2012.11.009
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