Gene transcription has distinct initiation, elongation and termination phases. The elongation phase, when DNA is copied into RNA, may be an important point of regulation in the gene transcription cycle. For example, HIV transcription is regulated at this stage by its Tat protein. During the elongation phase, RNA polymerase II must overcome the repeating barrier to its progress along the gene that is imposed by nucleosomes. In addition, the activity of the elongating RNA polymerase II is coupled to RNA processing reactions, including splicing and mRNA export that may occur or be initiated during transcription. Purified RNA polymerase II is incapable of transcribing through nucleosomes on its own, which indicates that it requires other factors to overcome the nucleosomal barrier to transcription. Likewise, there is evidence that accessory factors that associate with RNA polymerase II may influence RNA processing reactions. This proposal concerns one such accessory factor, the Spt4-Spt5 complex. The Spt4-Spt5 complex is essential for life, is found in all eukaryotes, and is implicated in the function of the HIV Tat protein. This study has three goals. The first is to carefully investigate the structure and function of the Spt4-Spt5 complex. Specific topics of investigation include the role of Spt4 in the complex, the ability of the complex to bind RNA, the nature of the interactions of the complex with RNA polymerase II and the regulation of Spt4-Spt5 function. The second goal is to gain a better understanding of how Spt4-Spt5 function is connected to chromatin. Studies here include investigation of direct interactions with histones and nucleosomes, genetic tests of the roles of histone methylation in Spt4-Spt5 function, and a genetic screen for other chromatin factors that influence Spt4-Spt5 function. The third goal is to analyze the role of Spt4-Spt5 in RNA processing focusing specifically on splicing and mRNA export. Studies here include biochemical and genetic analyses of splicing in spt mutants and tests of the influence of Spt4-Spt5 on the assembly of RNA export proteins onto mRNA.
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