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Abstract
The human genome is packaged into higher order structures by wrapping the DNA around histone proteins to form chromatin. Interaction of DNA with histones, i.e. nucleosome positioning, affects how a cell utilizes a given sequence of DNA, either by enhancing or repressing gene expression. Chromatin is in constant flux during cell differentiation and embryogenesis as genes are activated or repressed depending on the function of the cell, yet many of these important changes have yet to be described in detail, especially nucleosome positioning. Therefore, we set out to characterize these changes at the promoter of SOX2 (Sry-box 2), a critical transcription factor in stem cell maintenance, through multiple stages of differentiation as well as in karyotypically abnormal cancer cells. These experiments demonstrate three distinct chromatin states near the transcription start site, repressed, poised, and active, which correspond to changes in nucleosome positioning, DNA methylation, and histone modifications.