Transactivation of Fetal Hemoglobin

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Sickle cell disease (SCD) is a common genetic disease that affects millions of people worldwide; it impacts one of 400 African-Americans born each year. Treatments, such as hydroxyurea (HU), that induce fetal hemoglobin (HbF), have enormous benefit to patients suffering from this hemoglobinopathy, since sustained expression of the ?-globin genes is palliative to these diseases, likely by preventing red blood cell (RBC) sickling and subsequent occlusion of blood vessels. However, HU has negative side effects and may be carcinogenic with long-term use. In addition, it stands alone as the only effective treatment for SCD developed in the last decade. Developmental regulation of human ¿-like globin gene switching is controlled by several parameters, primarily the trans-acting transcriptional milieu and cis-acting DNA elements. Unraveling the mechanisms underlying control of globin gene expression, particularly those involved in activation of ?- globin synthesis is important for discerning new targets for therapeutic intervention. The human proteins, testis-specific protein, Y-encoded-like (TSPYL1) and fetal globin inducing factor (FGIF or ANKRD49), have been shown to up-regulate ?-globin gene expression. The overall goal of this proposal is to explore the usefulness of these two proteins as therapeutic targets in treating SCD by determining their mechanisms of action, so that ultimately novel therapies can be developed that target the regulation of these proteins. For Specific Aims 1 and 2, we will use enforced expression (gain-of-function) or knockdown of expression (loss-of function) of TSPYL1 and FGIF in erythroid cells to ascertain phenotypic or developmental effects in vivo. We will employ chromatin immunoprecipitation (ChIP) to determine the sequences near the ?-globin genes where TSPYL1- or FGIF-containing complexes bind, and identify the partner proteins that TSPYL1 or FGIF interact with using immunoprecipitation (IP) coupled with mass spectrometry. It is improbable that all classes of proteins involved in ?-globin gene activation have been uncovered, leaving many more beneficial therapeutic targets still to be discovered. Thus, for Specific Aim 3, we will employ a novel selection system based on activation of an A?-globin promoter-green fluorescent protein (GFP) fusion in ¿-globin locus yeast artificial chromosome (¿-YAC) bone marrow cells (BMCs) derived from transgenic mice to identify new transactivators of ?-globin synthesis that may or may not partner with TSPYL1 or FGIF. Completion of these studies will provide important animal models and biochemical data to further understand the function of TSPYL1 and FGIF in up-regulating ?-globin gene expression during development. This proposal will generate unique tools and new strategies to understand mechanisms of ?-globin gene regulation for treatment of SCD.