Cover photograph (Copyright © 2000, American Society for Microbiology. All rights reserved.): A chimeric protein consisting of an adeno-associated virus Rep68 mutant protein fused with a truncated form of the hormone binding domain of the progesterone receptor is specifically activated by the synthetic steroid RU486, which also affects the intracellular distribution of the fusion protein. The figure shows an immunostained cell. In the presence of RU486, the chimeric protein (blue) is evenly distributed between the nucleus and cytoplasm. (See related article in January 2000, issue 1: vol. 74, p. 281.)