| dc.description.abstract | ISWI (Imitation Switch) family of chromatin remodeling complexes mobilize nucleosomes to control DNA accessibility, which manages various DNA template-associated processes like replication, transcription, and repair. Analysis of glioblastoma (GBM) transcriptome data sets (n=10) revealed that BAZ1A (Bromodomain Adjacent To Zinc Finger Domain 1A) is the highly expressed member of the ISWI family in GBM. Depletion by short-hairpin RNA (shRNA) or inhibition by a pharmacological inhibitor inhibited the survival and migration of established glioma cells and glioma stem-like cells (GSCs), sensitized glioma cells to Temozolomide (TMZ) but could not affect immortalized human astrocytes. Mechanistically, BAZ1A deficiency arrested cells in the G1 phase and induced programmed cell death. Gene Ontology (GO) analysis of differentially regulated genes in BAZ1A silenced cells showed enrichment of terms related to cell cycle processes, chromatin, and ATP binding. Further, Gene Set Enrichment Analysis (GSEA) showed a significant depletion of the “HALLMARK_E2F_TARGETS” gene set. We showed that BAZ1A silencing hindered the transcription from E2F-dependent promoter-reporters and reduced the transcript levels of E2F1 and E2F2 and several E2F target genes. The transcript level of BAZ1A is positively correlated with E2F genes and E2F target genes. Interestingly, immunoblot analysis of BAZ1A silenced cells identified E2F1 as the primary target. Chromatin Immunoprecipitation (ChIP) experiments revealed that the E2F1 promoter is bound by BAZ1A and E2F1. Additionally, SMARCA1/5, ATPase subunits of the ISWI family, showed occupancy to the E2F1 promoter region. BAZ1A depletion decreased the DNase1 sensitivity of the E2F1 promoter, suggesting condensed chromatin at the E2F1 promoter region. We have also demonstrated that BAZ1A, SMARCA5, and E2F1 interact in a protein complex via co-immunoprecipitation assay. Finally, we showed that BAZ1A silencing inhibited glioma tumor growth in a xenograft mouse model. In conclusion, our results demonstrate for the first time that BAZ1A containing ISWI complex interacts with E2F1 and recruits E2F1 to E2F1 promoter to activate the E2F transcription program, thus promoting G1-S progression and establishing BAZ1A as a potential therapeutic target. | en_US |
