In the PNAS Early Edition this week, the University of Chicago's Yong Woo and Wen-Hsiung Li describe the relationships among the "gene clustering pattern, promoter architecture, and gene expression stability in eukaryotic genomes." In a budding yeast model, Woo and Li found that "genes with a short upstream distance tend to have low gene expression variability, and their [promoters are] flanked by strongly positioned nucleosomes and [tend] to have low nucleosome occupancy." The pair also reports that head-to-head genes, when compared with head-to-tail genes, show