Complex sentence: Bivalent chromatin are segments of DNA, bound to histone proteins that have both repressing and activating epigenetic regulators in the same region that work to enhance or silence the expression of genes.
Split into simpler sentences: Bivalent chromatin are segments of DNA, bound to histone proteins, that have both repressing and activating epigenetic regulators in the same region. These regulators that work to enhance or silence the expression of genes.