Restricting centriole duplication to once per cell cycle is critical for chromosome segregation and genomic stability, but the mechanisms underlying this block to reduplication are unclear. Genetic analyses have suggested an involvement for Skp/Cullin/F box (SCF)-class ubiquitin ligases in this process. In this study, we describe a mechanism to prevent centriole reduplication in Drosophila melanogaster whereby the SCF E3 ubiquitin ligase in complex with the F-box protein Slimb mediates proteolytic degradation of the centrosomal regulatory kinase Plk4. We identified SCFSlimb as a regulator of centriole duplication via an RNA interference (RNAi) screen of Cullin-based ubiquitin ligases. We found that Plk4 binds to Slimb and is an SCFSlimb target. Both Slimb and Plk4 localize to centrioles, with Plk4 levels highest at mitosis and absent during S phase. Using a Plk4 Slimb-binding mutant and Slimb RNAi, we show that Slimb regulates Plk4 localization to centrioles during interphase, thus regulating centriole number and ensuring the block to centriole reduplication.

APC is a key tumor suppressor and Wnt signaling regulator, but its mechanism of action remains mysterious. We combined parallel assays in Drosophila and cultured human colon cancer cell lines to test hypotheses regarding APC function and to develop novel hypotheses, using mutants altering its structure in specific ways.

Current estimates indicate that nearly a third of the world's population is latently infected with Mycobacterium tuberculosis. Reduced oxygen tension and nitric oxide exposure are two conditions encountered by bacilli in vivo that may promote latency. In vitro exposure to hypoxia or nitric oxide results in bacterial stasis with concomitant induction of a 47-gene regulon controlled by the transcription factor DosR. In this report we demonstrate that both the dosS gene adjacent to dosR and another gene, dosT (Rv2027c), encode sensor kinases, each of which can autophosphorylate at a conserved histidine and then transfer phosphate to an aspartate residue of DosR. Mutant bacteria lacking both sensors are unable to activate expression of DosR-regulated genes. These data indicate that DosR/DosS/DosT comprise a two-component signaling system that is required for the M. tuberculosis genetic response to hypoxia and nitric oxide, two conditions that produce reversible growth arrest in vitro and may contribute to latency in vivo.Tuberculosis (TB) 1 has placed a heavy burden on the global community for centuries, earning such morbid nicknames as The White Plague and The Captain of the Men of Death (1). The causative agent, Mycobacterium tuberculosis (MTB), kills about 2 million people annually making it a leading cause of infectious death worldwide (2, 3). The success of MTB as a pathogen is closely linked with its capacity to persist for years or decades in humans in the absence of any clinical disease symptoms. Current estimates place the number of people latently infected with MTB at nearly 2 billion, or one-third of the Earth's population (3, 4). Eradicating this enormous reservoir of latently infected carriers is complicated by several factors, including the availability, cost, and length of drug therapy required for successful treatment of latent TB.Although TB has been studied for centuries, the triggers that promote and maintain latent infections are still obscure. Two conditions frequently associated with latent TB in vivo are reduced oxygen tension and nitric oxide (NO) exposure (5, 6). Both of these stimuli can induce reversible bacterial stasis in vitro (7,8), and both are encountered by bacilli in vivo (5, 9, 10). Further, although MTB requires oxygen for growth, it can survive without oxygen for surprisingly long periods of time (11,12). Still the evidence linking hypoxia and NO to latent TB in vivo remains circumstantial. Analysis of the MTB response to these factors is needed to define the role they may play in promoting and maintaining TB latency in humans.Previous reports identified a set of 47 MTB genes that are rapidly up-regulated in response to reduced oxygen tension or NO (8, 13). Among the MTB genes induced by hypoxia or exposure to NO is the putative two-component regulatory system dosR-dosS (also called devR-devS, Rv3133c/Rv3132c 2 ) (8, 13). In bacteria, two-component response regulator systems are an important means by which a variety of environmental signals are transduced into a phenotypic respo...

Fruit flies of the genus Drosophila have been an attractive and effective genetic model organism since Thomas Hunt Morgan and colleagues made seminal discoveries with them a century ago. Work with Drosophila has enabled dramatic advances in cell and developmental biology, neurobiology and behavior, molecular biology, evolutionary and population genetics, and other fields. With more tissue types and observable behaviors than in other short-generation model organisms, and with vast genome data available for many species within the genus, the fly's tractable complexity will continue to enable exciting opportunities to explore mechanisms of complex developmental programs, behaviors, and broader evolutionary questions. This primer describes the organism's natural history, the features of sequenced genomes within the genus, the wide range of available genetic tools and online resources, the types of biological questions Drosophila can help address, and historical milestones.