"During the first step of gene expression, RNA Polymerase (RNAP) transcribes RNA from a DNA template in every living cell. Crystal structures of RNAP core as well as RNAP elongation complexes (ECs) have revolutionized our understanding of transcription. This groundwork paved the way for more complex questions addressing the regulation of transcription. Because of its fundamental role, transcriptional regulation has an impact on every aspect of biology including a growing list of human diseases. Thus, a detailed and mechanistic understanding is crucial and this is the area where the work proposed here will contribute. A combination of biochemistry and structural approaches (primarily X-ray crystallography) will be used to gain detailed understanding on the regulation of transcription by protein factors and non-coding RNAs. To complement the structural and biochemical results, Fluorescence Resonance Energy Transfer (FRET) studies will be used to study the dynamics of RNAP during processes that regulate transcription such as transcriptional pausing. The FRET assay will also be used to test hypotheses regarding the recognition of errors made by RNA polymerase."