More than 10 years ago, the discovery of cyclin-dependent ki- nases (Cdks) ushered in a new era in the understanding of cell proliferation and its control. Not only were both of the known cell cycle transitions, from G 1 to S phase and G2 to M phase, found to be dependent on these protein kinases, but the reg- ulatory assumption intrinsic to cyclin-dependent kinases, a stable inactive catalytic subunit (the Cdk) and an unstable requisite positive regulatory activating subunit (the cyclin), led to a simple model for cell cycle control. Modulation of cyclin accumulation, and thereby Cdk...

An integrated retrovirus effectively becomes part of the cellular genome, but with the difference that the virus to a large extent retains control over its own expression through nontranslated sequences in the long terminal repeat (L TR). Some retroviruses also code for nonstructural proteins that further regulate proviral expression. Integration changes the cell genome; it adds viral genes, and in the case of transducing retroviruses also adds cell-derived oncogenes that have been incorporated into the viral genome. Integration can also have consequences for cellular genes. The...

When it comes to bacterial disease, we are living in a state of false security. Antibiotics have indeed brought unprecedented health benefits, protection from and cure of bacterial diseases during the past 50 years. But there are ominous signs that the fortress and the defenses built on antibiotics are crumbling. They are crum- bling because we wittingly or unwittingly created selective con- ditions for the emergence of superior pathogens that can no longer be controlled by antibiotics. There are numerous warnings. After a long period of eclipse tuberculosis has now emerged as a serious...