Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Genetic analysis of Myc and telomerase interactions in vivo. Effects of conditional Myc activation in mice with wild-type telomerase, mice with constitutive telomerase overexpression, and mice deficient for telomerase and showing short telomeres, as determined by measuring bromodeoxyuridine incorporation in representative skin sections and telomere fluorescence by quantitative fluorescent in situ hybridization, are shown. Note that telomerase overexpression cooperates with Myc in inducing papillomatosis in the absence of changes in telomere length. In contrast, telomerase deficiency and short telomeres severely impair Myc-induced papillomatosis. (See related article in August 2006, vol. 26: issue 16, p. 6130.)