Interaction of E2F3a and CASP8AP2 Regulates Histone Expression and Chemosensitivity of Leukemic Cells

Low expression levels of E2F3a and caspase 8-associated protein 2 (CASP8AP2) are associated with poor outcomes in children with acute lymphoblastic leukemia. Our previous study showed that a combined assessment of E2F3a and CASP8AP2 expression was more accurate in predicting relapse in children with acute lymphoblastic leukemia. However, the underlying mechanism remains unclear. In this study, the interaction between E2F3a and CASP8AP2 and its role in the regulation of histone expression, cell proliferation, the cell cycle, and chemosensitivity were investigated. Exogenous E2F3a-GST was coprecipitated with CASP8AP2-FLAG in HEK-293T cells. E2F3a was colocalized with CASP8AP2-GFP in the nucleus. The replication-dependent histones H2A and H2B were significantly upregulated when E2F3a or CASP8AP2 was overexpressed in HEK-293T or 697 cells and downregulated by E2F3a or CASP8AP2 knockdown. E2F3a and CASP8AP2 could collaboratively enhance the transcriptional activity of HIST1H2AG and HIST1H2BK. Both CASP8AP2 and E2F3a are involved in S phase progression. E2F3a and CASP8AP2 also affected the sensitivity of leukemic cells to daunorubicin. Therefore, CASP8AP2 and E2F3a collaboratively regulated replication-dependent histone expression, cell cycle progression, and chemosensitivity of leukemic cells.