6.3.4.10	down	evolutionary conserved binding site for microRNA miR-539 in the 3'-untranslated region of HCS mRNA. miR-539 decreases the expression of HCS at the level of transcription rather than translation. When miR-539 is overexpressed in transgenic cells, the abundance of both HCS and biotinylated histones decreases. The abundance of miR-539 is tissue dependent, decreasing in the order fibroblasts, kidney cells, intestinal cells, lymphoid cells. The abundance of miR-539 is significantly higher at physiological concentrations of biotin than both biotin-deficient and biotin-supplemented media in all cell lines tested	715999