Mechanisms of recruitment and roles of the BET family chromatin readers in transcription initiation

Oklahoma Medical Research Foundation, Oklahoma City OK

Investigators

Abstract

Abstract Accurate regulation of transcription is critical for gene expression and has a significant impact on cell growth, proliferation, and differentiation. Perturbations in transcriptional programs are the common cause of the emergence and progression of human diseases. Despite the recent advances in understanding of how basic transcriptional machinery operates, it remains elusive how transcriptional programs are regulated genome-wide by a coordinated action of chromatin dynamics, sequence-specific transcription factors, and coactivators. Chromatin readers are important for gene regulation due to their ability to translate epigenetic modifications on histones into specific transcriptional output. Chromatin readers from the bromodomain and extra-terminal domain (BET) family are essential for transcription of most genes in healthy eukaryotic cells, and they are implicated in sustaining pathological transcriptional programs in many human conditions. Despite their significant impact on transcription and other chromatin-based processes, the roles and regulation of BET factors are poorly understood. Importantly, it remains elusive what features of their biology are gene, tissue, or disease specific, and what features are generally required for transcription. We recently found that yeast BET proteins, Bdf1 and Bdf2, have functions that are highly similar to their human homologues, which indicates that many aspects of BET biology are conserved across eukaryotes. Our proposed work will reveal the mechanisms by which BET proteins are recruited to chromatin and regulate transcription initiation. Based on our prior results and preliminary findings, we hypothesize that transcription initiation is a major step of transcription influenced by BET proteins and that the interplay between BET proteins and selected transcriptional coactivators and protein complexes involved in chromatin dynamics is at the center of this regulation. To address these questions, we will focus on two main aims. We will: 1) Determine the BET protein interaction network. Based on current understanding, the complex roles of BET proteins are largely mediated through interactions with other factors. We will define the BET protein interaction network using a combination of proteomic and molecular biology approaches. 2) Determine the mechanisms of BET proteins in transcription initiation. Canonical models assert that as chromatin readers, BET proteins are recruited to chromatin by their bromodomains. However, it is less clear how BET proteins affect transcription once recruited, and recent evidence suggests that bromodomain activity alone does not fully explain recruitment. We will address this knowledge gap by a functional dissection of all conserved domains of BET proteins and by characterization of a crosstalk of BET proteins with regulatory complexes. These studies will be based on yeast genetics, molecular biology, and genomic methods I applied in my past work, as well as on new approaches including proteomic technologies. The expected outcomes of this project will have important implications for models of transcriptional regulation in eukaryotes and will provide a foundation for the long-term growth of our research program.