Bcl11b transcription factor regulation by phosphorylation and sumoylation

Filtz, Theresa

Abstract

Cellular growth, maturation and transformation, among other functions, require the translation of extracellular signals into altered programs of gene expression. The key translators for these signals are transcription factor proteins. Bcl11b is a transcription factor that is critical for the development and function of several organ systems, including the immune and central nervous systems, skin, and craniofacial structures. Importantly, dysregulation of Bcl11b is strongly associated with T-cell acute lymphoblastic leukemia (T-ALL), an aggressive childhood cancer, and acceleration to the lethal blast crisis stage in a mouse model of chronic myelogenous leukemia (CML). The mechanism whereby loss of Bcl11b leads to tumor progression is not understood. In addition, the means by which extracellular signals impinge on transcriptional factors to regulate the transcriptome, in development or neoplastic transformation, is also poorly understood. The long-term goal of this laboratory is to elucidate the mechanisms by which signal transduction pathways regulate transcription factor activities with the goal of altering this regulation for treatment of human diseases. Bcl11b is richly modified by activation of the MAP kinase pathway in thymocytes, and its activity varies from gene repressor to activator dependent upon stimulation. Thus, Bcl11b not only has relevance to human disease, but is an excellent model to study the relationship between sub-molecular structural changes and transcription factor function. The goal of this proposal is to identify the stimulated, post-translation modifications of Bcl11b, and to understand the relationship between varying modified states of Bcl11b and its varied activities. For these studies we will use advanced mass spectrometry techniques, site-directed mutants, over expression and knockdown. Upon successful completion of our specific aims, we will provide a methodological blueprint for others seeking to understand the importance of the temporal organization of amino acid-level modifications of richly decorated transcription factors. Our findings should also highlight potential molecular targets for development of novel therapies in leukemia and perhaps other T cell-associated disorders. We also expect to better understand the regulation of Bcl11b in thymocyte maturation and to apply our findings to other organ systems. Finally, we will train a next generation of students in 21st century biomedical research techniques.

Public Health Relevance

We wish to ultimately understand how to manipulate the gene expression changes leading to T cell cancers and in T cell development. To this end we are studying Bcl11b, an important regulator of gene expression in the immune cells and neurons. Bcl11b is dysregulated in certain T cell leukemia, and mice that lack Bcl11b have an incomplete immune system that lacks mature T cells among other defects. We wish to understand how the activity of Bcl11b is controlled at a molecular level in T cells to begin to understand its control of gene expression.