Organisms develop in precisely organized patterns that are controlled by complex cellular mechanisms. Many of these mechanisms are conserved throughout higher eukaryotes. Some proteins are responsible for directing the development of specific parts of the body (e.g. homeotic proteins). Others, such as RNA helicase A (RHA), are involved in basic cellular processes in all cells, and defects in these proteins produce developmental abnormalities throughout the organism. RNA helicases are involved in various steps of mRNA metabolism, such as transcription and splicing. Helicases use energy from A1'P hydrolysis to separate duplex nucleic acids into single strands. RNA helicase A is essential for proper development in mice, flies, and the model organism C. elegans. Its precise cellular function is unknown, but in vitro experiments with the human RHA homolog provide some clues. For example, human RHA is required for the in vitro transcription activation of RNA polymerase II by CBP, a protein involved in cAMP signaling in the cell. Mutations in CBP cause the human disease Rubinstein-Taybi syndrome, which is associated with developmental abnormalities such as broad digits and mental retardation. Human RHA is also responsible for genomic viral RNA export from the nucleus. In order to determine the precise cellular function of RHA, this proposal involves biochemical and genetic studies of RHA- 1, the RHA homolog in C. elegans. RNA binding, ATPase, and RNA helicase properties of RHA-1 will be studied in vitro using purified protein and well-defined RNA substrates. Candidate proteins that may bind to RHA- 1 in the cell will be tested using the yeast two-hybrid system. These binding partners may reveal the cellular function of RHA-1 and they may alter the biochemical activity of RHA- 1. Finally, worms with reduced function of RHA- 1 and/or its binding partners will be generated to determine the physiological function of RHA-1. The ultimate goal is to determine the cellular function of RHA-1 to obtain a better understanding of how transcription and mRNA processing affect the development in all eukaryotes, including humans.