To analyze the leukemogenic process and to create model mice for t(17;19)-positive leukemia, we generated inducible knock-in (iKI) mice for E2A-HLF.     ///     E2A-hepatic leukemia factor (HLF) is a chimeric protein found in B-lineage acute lymphoblastic leukemia (ALL) with t(17;19).     ///    "Inverse PCR detected three common integration sites specific for E2A-HLF iKI leukemic mice, which induced overexpression of zinc-finger transcription factors: growth factor independent 1 (Gfi1), zinc-finger protein subfamily 1A1 isoform a (Zfp1a1, also known as Ikaros) and zinc-finger protein 521 (Zfp521). "    ///    Identification of Zfp521/ZNF521 as a cooperative gene for E2A-HLF to develop acute B-lineage leukemia..     ///    "Moreover, both iKI for E2A-HLF and transgenic for Zfp521 mice frequently developed B-lineage ALL. "    ///    "Despite the induced expression of E2A-HLF in the hematopoietic tissues, no disease was developed during the long observation period, indicating that additional gene alterations are required to develop leukemia. "    ///    Virus infection induced acute leukemias in E2A-HLF iKI mice with higher morbidity and mortality than in control mice.     ///    "To elucidate this process, E2A-HLF iKI and control littermates were subjected to retroviral insertional mutagenesis. "