Cover photograph (Copyright © 2003, American Society for Microbiology. All Rights Reserved.): The SET oncoprotein is present at transcriptionally active loci where histone H3 is also phosphorylated in the Ser10 residue. Antibodies were used to detect the distribution of SET protein (red) and the Ser10-phosphorylated histone H3 isoform (green) in polytene chromosomes prepared from wild-type Drosophila larvae. Regions of overlap are shown in yellow. Chromosome spreads were also counterstained with 4`,6-diamidino-2-phenylindole (blue) to view the DNA. The SET protein is detected at puffed and H3-phosphorylated (transcriptionally active) loci, including the ecdysone-regulated genes. (See related article on p. 6129.)