Chromatin Immunoprecipitation (ChIP) assays were conducted to test whether the CBX7 could bind to the CCNE1 promoter in glioma cells. Protein-chromatin complexes were subjected to immunoprecipitation with anti-CBX7 or anti-IgG antibodies and then the precipitate was analyzed using reverse transcription-PCR (RT-PCR) and quantitative real-time-PCR (q-PCR) (Figure 4E and 4F). Then, U87 and LN229 cells with exogenous expression CBX7 protein were used to further assess the interaction between CBX7 and CCNE1 promotor. Along with the increased CBX7 levels, the enrichment of precipitated CCNE1 promotor fragment was ascending (Figure 4G). To verify the interaction between CBX7 and HDAC2, lysates of U251, U87 and LN229 cells were subjected to IP with anti-CBX7 antibodies or nonspecific IgG. The immunocomplexes were immunoblotted with anti-HDAC2 antibodies. Conversely, anti-HDAC2 antibodies were used to pull down the proteins combine to HDAC2. Then, the immunocomplexes were immunoblotted with anti-CBX7 antibodies to ascertain that HDAC2 combines to CBX7. Using co-immunoprecipitation (coIP) assays, we confirmed that CBX7 interacted with HDAC2 (Figure 4H). We tested the degree of histone acetylation and cyclin E1 levels in three GBM cell lines treated with 1μM HDCA2 inhibitor FK228 for 24 h and found that inhibition of HDAC2 rescued the levels of cyclin E1 (Figure 4I).