Figure 4. SOCS1 overexpression degraded P21 via ubiquitin. (A) Histochemical staining and TUNEL detection of tumour-bearing tissues in nude mice. (B) The mRNA levels of P21 and P27 are not regulated by SOCS1. (C) The ubiquitin inhibitory effect of 20 μM MG-132 (a proteasome inhibitor) on SMMC-7721 and HCC-LM3 cells was observed at 2 hours, 4 hours, 6 hours and 8 hours. (D) Detection of the difference in ubiquitination of P21 after overexpression of SOCS1 by Co-IP. (E) Interaction network between SOCS1, ubiquitin proteins, cyclin proteins and cyclin-dependent kinases.