TY - JOUR T1 - A synthetic biology approach to probing nucleosome symmetry JF - bioRxiv DO - 10.1101/170811 SP - 170811 AU - Yuichi Ichikawa AU - Caitlin F. Connelly AU - Alon Appleboim AU - Hadas Jacobi AU - Nebiyu A. Abshiru AU - Hsin-Jung Chou AU - Yuanyuan Chen AU - Upasna Sharma AU - Yupeng Zheng AU - Paul M. Thomas AU - Hsiuyi V. Chen AU - Vineeta Bajaj AU - Neil L. Kelleher AU - Nir Friedman AU - Daniel N. Bolon AU - Oliver J. Rando AU - Paul D. Kaufman Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/07/31/170811.abstract N2 - The repeating subunit of chromatin, the nucleosome, includes two copies of each of the four core histones, and several recent studies have reported that asymmetrically-modified nucleosomes occur at regulatory elements in vivo. To probe the mechanisms by which histone modifications are read out, we designed an obligate pair of H3 heterodimers, termed H3X and H3Y, which we validated genetically and biochemically. Comparing the effects of asymmetric histone tail point mutants with those of symmetric double mutants revealed that a single methylated H3K36 per nucleosome was sufficient to silence cryptic transcription in vivo. We also demonstrate the utility of this system for analysis of histone modification crosstalk, using mass spectrometry to separately identify modifications on both H3 molecules within asymmetric nucleosomes. The ability to generate asymmetric nucleosomes in vivo provides a powerful tool to probe the mechanism by which H3 tails are read out by effector proteins in the cell. ER -