Several lysine residues in p53 C -terminus have been identified as the sites of ubiquitination , and it has been shown that p53 protein levels are downregulated by Mdm2 in a proteasome-dependent manner .
ADJ NOUN NOUN ADP NOUN PROPN PROPN AUX AUX VERB ADP DET NOUN ADP NOUN , CCONJ PRON AUX AUX VERB SCONJ NOUN NOUN NOUN AUX VERB ADP NUM ADP DET ADJ NOUN .