β-Lactam resistance in Staphylococcus aureus: the adaptive resistance of a plastic genome

Staphylococci have two mechanisms for resistance to β-lactam antibiotics. One is the production of β-lactamases, enzymes that hydrolytically destroy β-lactams. The other is the expression of penicillin-binding protein 2a (PBP 2a), which is not susceptible to inhibition by β-lactam antibiotics. Strains of S. aureus exhibiting either β-lactamase or PBP 2a-directed resistance (or both) have established a considerable ecological niche among human pathogens. The emergence and subsequent spread of bacterial strains designated as methicillin-resistant S. aureus (MRSA), from the 1960s to the present, has created clinical difficulties for nosocomial treatment on a global scale. The recent variants of MRSA that are resistant to glycopeptide antibiotics (such as vancomycin) have ushered in a new and disconcerting chapter in the evolution of this organism. Received 2 April 2005; received after revision 15 July 2005; accepted 25 July 2005     

The origins and uses of mouse outbred stocks

Outbred mouse stocks, often used in genetics, toxicology and pharmacology research, have been generated in rather haphazard ways. Understanding the characteristics of these stocks and their advantages and disadvantages is important for experimental design. In many studies these mice are used inappropriately, wasting animals' lives and resources on suboptimal experiments. Recently, however, researchers from the field of complex trait analysis have capitalized on the genetics of outbred stocks to refine the identification of quantitative trait loci. Here we assess the most widely used outbred stocks of mice and present guidelines for their use.     

A mutation in stratifin is responsible for the repeated epilation (Er) phenotype in mice

Stratifin (Sfn, also called 14-3-3sigma) is highly expressed in differentiating epidermis and mediates cell cycle arrest. Sfn is repressed in cancer, but its function during development is uncharacterized. We identified an insertion mutation in the gene Sfn in repeated epilation (Er) mutant mice by positional cloning. Er/+ mice expressed a truncated Sfn protein, which probably contributes to the defects in Er/Er and Er/+ epidermis and to cancer development in Er/+ mice.     

Changes in beta-2 adrenergic receptor sensitivity with maturation of erythroid progenitor cells

Summary Erythroid burst forming units (BFU-E) were much more sensitive to the beta-2 selective adrenergic drug, salbutamol, than erythroid colony forming units (CFU-E) in an in vitro study of erythroid progenitor cells.This work was supported by USPHS Grant AM13211. B. Beckman is a USPHS Postdoctoral Fellow AM05960.     

The trans-activator gene of HTLV-III is essential for virus replication

Studies of the genomic structure of human T-lymphotropic virus type III (HTLV-III) and related viruses, implicated as the causal agent of acquired immune deficiency syndrome (AIDS), have identified a sixth open reading frame in addition to the five previously known within the genome (gag, pol, sor, env and 3'orf). This gene, called tat-III, lies between the sor and env genes and is able to mediate activation, in a trans configuration, of the genes linked to HTLV-III long terminal repeat (LTR) sequences. We now present evidence that the product of tat-III is an absolute requirement for virus expression. We show that derivatives of a biologically competent molecular clone of HTLV-III, in which the tat-III gene is deleted or the normal splicing abrogated, failed to produce or expressed unusually low levels of virus, respectively, when transfected into T-cell cultures. The capacity of these tat-III-defective genomes was transiently restored by co-transfection of a plasmid clone containing a functional tat-III gene or by introducing the TAT-III protein itself. As HTLV-III and related viruses are the presumed causal agents of AIDS and associated conditions, the observation that tat-III is critical for HTLV-III replication has important clinical implications, and suggests that specific inhibition of the activity of tat-III could be a novel and effective therapeutic approach to the treatment of AIDS.