Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights reserved.): Simultaneous loading of multiple nucleoside triphosphate (NTP) substrates by human RNA polymerase II. Template DNA, green; nontemplate DNA, yellow; RNA, orange; i+1 NTP, dark blue (phosphates, white); i+2 NTP, light blue; i+3 NTP, pink; bridge α-helix, silver; active-site metals, magenta; basic amino acids, dark blue; acidic amino acids, red; hydrophobic amino acids, white. The image was derived from the yeast RNA polymerase II elongation complex structure and was prepared by X. Q. Gong. (See related article on p. 3583.)