Cover photograph (Copyright © 2003, American Society for Microbiology. All Rights Reserved.): Transient expression of the human papillomavirus type 16 (HPV-16) E7 oncoprotein in mouse embryo fibroblasts (MEFs) deficient for all three retinoblastoma protein family members, pRb, p107, and p130, induces the formation of abnormal numbers of centrosomes. At 48 h after transfection of the HPV-16 E7 gene, cells were analyzed by immunofluorescence microscopy for the pericentrosomal marker γ-tubulin (green). Nucleus is stained blue, and mitochondria are stained red. (See related article on page 12331.)