Cover photograph (Copyright © 2003, American Society for Microbiology. All Rights Reserved.): Asymmetric recognition of AP-1 sites influences transcriptional cooperativity. The upper image shows the fluorescence emissions of complexes formed by Fos, Jun, ATF2, and NFAT1 at composite regulatory elements separated in a polyacrylamide gel (gelFRET analysis). The differences in color reflect differences in fluorescence resonance energy transfer between heterodimers bound in opposite orientations. The diagrams below show the influence of the orientation of Fos (red)-Jun (blue) heterodimer binding on their interactions with NFAT1 (green) and transcription activation (bent arrows). (See related article by V. Ramirez-Carrozzi and T. Kerppola in the next issue.)