In vivo analysis of transcription elongation factors in Drosophila melanogaster

Understanding the mechanisms that regulate the transcription of eukaryotic genes is among the major challenges in modern biology and biochemistry. In eukaryotes, the synthesis of messenger RNA (mRNA) is catalyzed by the multisubunit enzyme, RNA polymerase II (Pol II). The transcription cycle proceeds through several stages, termed preinitiation, initiation, promoter clearance, elongation and chain termination. Each phase of this cycle is regulated by a number of proteins, collectively referred to as transcription factors.; During the last decade, a variety of protein factors have been biochemically characterized based on their ability to increase the overall catalytic rate of transcription elongation by Pol II in vitro. Among these factors are the ELL and Elongin families of proteins. The ELL gene was originally cloned as a translocation partner of the MLL gene in a significant percentage of patients with acute myeloid leukemia. Understanding how this translocation results in leukemogenesis is among the major goals of our laboratory. By understanding the biochemical in vivo properties of ELL, perhaps we can gain insights into its role in leukemogenesis when fused to the MLL protein.; The heterotrimeric Elongin complex was initially purified and characterized biochemically based on its ability to stimulate Pol II elongation in vitro. Elongin A, the largest component of the complex, is the transcriptionally active component, while the smaller B and C components appear to play regulatory roles. While much is known about the in vitro properties of Elongin A and other members of this class of elongation factors, the physiological role(s) of these proteins remain largely unclear.; Recently, we identified Drosophila homologues of both the ELL family (dELL) and the Elongin A family (dEloA). We have studied the properties of dELL and dEloA using this in vivo model system. We demonstrate that these proteins interact functionally with Pol II in vivo. Further, we show that these factors have non-redundant functions during fly development and are required for the expression of specific genes.