<p><b>A.</b> HEK293 cells were co-transfected with FLAG-GCH1 and HA tagged ubiquitin plasmids (HA-Ub) for 2 days, cells were lysed, and the proteins were analyzed by immunoblotting using the indicated antibodies. The double plus symbol (<b>++</b>) indicates two folds of HA-Ub plasmids. HEK293 cells were co-transfected with FLAG-GCH1 plasmids and <b>B.</b> Lys48-only ubiquitin plasmids (K48 only-Ub) or, <b>C.</b> Lys63-only ubiquitin plasmids (K63 only-Ub). <b>D.</b> Compare of the GTPCH1 level with or without ubiquitin plasmids overexpression. The blot shown is representative of three independent experiments. Data are shown as mean±standard deviation (n = 3). *<sup>#</sup><i>P</i><0.05 vs. control (without ubiquitin plasmids overexpression). NS indicates <i>P</i>>0.05 vs. control.</p
