The overall goal of this project is to offer novel insights into the mechanisms of epigenetic deregulation in hematological malignancies that may lead to improved therapeutic strategies. Leukemias bearing chromosomal rearrangements of the AF10 transcription factor are marked by specific perturbations of chromatin 1-3, thereby providing an excellent model for the study of epigenetic deregulation in oncogenesis. We hypothesize that epigenetic dysregulation in the AF10 leukemias results from the loss of the N-terminal PHD domains of AF10 and the retention of the C-terminal octapeptide motif-leucine zipper (OM-LZ) domain in oncogenic AF10 fusions. Our preliminary observations show that transformation by AF10 fusion oncogenes can be suppressed by inhibiting the activity of the AF10 OM-LZ domain or alternatively, by restoring the PHD zinc finger domain in oncogenic AF10 fusions. These observations hold great therapeutic promise for the AF10 leukemias. In Specific Aim 1, we propose to identify mechanisms that lead to tumor suppression using established models of leukemia and knockout mice, followed by high throughput approaches. The clinical relevance of these studies is borne out by the fact that AF10 is involved in recurrent chromosomal translocations in a wide variety of hematological malignancies 4-8. Moreover, several other cancers share features common to the AF10 leukemias, notably - involvement of PHD domains 9-12 or the histone methyltransferase DOT1L 13 together with deregulation of the developmentally critical HOX genes 14, 15. The proposed studies may therefore yield valuable insights into common mechanisms of HOX gene deregulation in cancer. Our preliminary results support a role for AF10 in the regulation of mammalian HOX genes. Deregulation of this function seems to be a critical event in oncogenesis of AF10 leukemias. Therefore, to gain insights into the role of AF10 in normal and leukemic hematopoiesis, we propose to identify the role of AF10 in normal and leukemic hematopoiesis using biochemical and gene-targeting approaches. Specifically, we plan to characterize the transcriptional activity of AF10 and establish conditional knockout mice with hematopoietic specific deletions of AF10 in Specific Aim 2. Prior studies support a role for AF10 in the regulation of HOX genes 1, 2, 16, 17. Establishment of AF10 knockout mice will enable assessment of AF10 function including potential regulation of HOX genes that have important roles in normal and malignant hematopoiesis. Since the AF10-DOT1L network is a valuable therapeutic target, identification of components of this network may provide critical information for its potential pharmacologic inhibition. The proposed project will be carried out in a rich academic institutional environment, and will be guided a mentoring committee composed of renowned scientists. The proposal is supported by a strong training component that includes didactic and practical instruction in epigenetics and hematopathology, training in the responsible conduct of research, and acquisition of mentoring abilities for successfully transitioning to an independent investigator.