Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Molecular models representing differential processes at heat shock gene promoters during induction. Purple, acetylated H3-enriched nucleosomes in the intermediate state at the HSP12 and HSP82 promoters; brown, nucleosomes with unacetylated H3; blue, inactive heat shock factor (HSF) in the uninduced state; red, activated HSF. Intermediate levels of HSF and RNA polymerase II loading are represented by scaled-down cartoons for the corresponding proteins. Histone displacement is represented by a diminishing amount of nucleosomes in the intermediate state. Intermediate-state cartoons roughly represent the situation at promoters after 2 minutes of heat shock. (See related article on p. 7587.)