Role of cohesin Stag1 during terminal erythropoiesis - Project Summary Understanding the molecular mechanisms that govern the transcriptional responses leading to hemoglobin synthesis during terminal erythropoiesis is critical, as the corruption of these mechanisms lead to ineffective erythropoiesis, a hallmark of diseases such as thallasemias and anemias. A clear understanding of the transcriptional mechanisms is paramount towards developing novel therapeutic interventions to treat these diseases, which are classified as major global health problems. Among the transcriptional regulators responsible for tissue differentiation processes are components of the cohesin complex, a ringlike structure made of SMC1A, SMC3, and RAD21 which binds to either Stag1 or Stag2. Recent reports have identified Stag1 mutations leading to childhood hematological malignancies and there is enrichment of Stag1 on the promoters of active genes in primary human erythroid cells11,12. Despite this, thus far, there is no report on the functional role of Stag1 on human terminal erythropoiesis. Our preliminary work shows that human Stag1 levels increase during terminal differentiation and that Stag1 levels, unlike those of its paralogue Stag2, regulate globin gene transcription. Cohesin ring components (SMC3) and Mediator1 binding to the promoters of globin genes decrease upon Stag1 depletion. We therefore hypothesize that Stag1 has roles in the regulation of globin gene expression during terminal erythropoiesis through genome architecture maintenance. To test our hypothesis, we propose the following aims: Specific Aim 1: To determine the domain requirements of Stag1 in its transcription regulation function. Specific Aim2: To interrogate the consequence of an acute Stag1 depletion on the terminal erythroid globin transcriptional output. Specific Aim3: To investigate whether Stag1 impacts globin promoter-enhancer interactions during terminal erythropoiesis The proposed study will aim to bridge the following gaps: 1. Address functional relevance of high Stag1 occupancy on the promoters of active genes during terminal erythropoiesis. 2. Delineate how paralogues of a cohesin subunit can drive specific functions during terminal erythroid differentiation. 3. Increase our understanding of the temporal dynamics of protein requirements, mediating the regulation of the adult globin genes during terminal erythroid differentiation.
