Fig 6.
Expression of GPC1 significantly upregulates cyclin E, CDK2, Skp2, and Cdt1 and downregulates Cip/Kip CKIs and CDH1. U87-MG cells were infected with different doses of control or GPC1 adenovirus for 48 h as indicated. Immunoblotting analysis for the indicated prominent cell cycle regulators was conducted. β-Actin was used as a loading control. Both cyclin E and CDK2 were significantly upregulated, while p21 and p27 were significantly downregulated, by ectopic expression of GPC1, pointing toward robust activation of CDK2, which may play a major role in G1/S checkpoint inactivation by GPC1 overexpression. The upregulation in Skp2 upon GPC1 transduction may contribute significantly to both p21 and p27 downregulation. Expression of GPC1 significantly downregulated CDH1 and upregulated Cdt1, which could contribute to premature entry into S phase and DNA replication relicensing, respectively.