Three forms of phosphatase type 1 in Swiss 3T3 fibroblasts. Free catalytic subunit appears to mediate s6 dephosphorylation

The major 40 S ribosomal protein S6 phosphatase in Swiss mouse 3T3 fibroblasts is a type 1 enzyme (Olivier, A. R., Ballou, L. M., and Thomas, G. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 4720-4724). Polyclonal antibodies were raised against a synthetic peptide containing the carboxyl-terminal 14 amino acids of the catalytic subunit of phosphatase 1 (PP-1C). Results from Western blot analysis and immunoprecipitation show that the peptide antiserum specifically recognizes PP-1C in cell extracts. Anion-exchange chromatography of cell extracts and Western blot analysis revealed three peaks of PP-1C termed A, B, and C. Peaks A and C are associated with the major type 1 S6 phosphatase activities, but peak B exhibits little activity. The phosphatase in peak A (Mr 39,000) appears to represent the free catalytic subunit, whereas the enzymes in peaks B and C display sizes of 68,000-140,000. Peak B contains two additional proteins of Mr 26,000 and 48,000 that co-immunoprecipitate with PP-1C, while peak C has a single additional protein of Mr 100,000. Fifteen min after serum withdrawal there is a 2-fold stimulation of S6 phosphatase activity in peak A that can be accounted for by an increase in the amount of PP-1C. The amount of PP-1C in the inactive peak B fraction also increases during this time and this increase is associated with changes in the phosphorylation state of the Mr 26,000 and 48,000 proteins. The results are discussed in relation to regulatory mechanisms which are thought to modulate the activity of type 1 phosphatase.     

Complex phylogenetic distribution of a non-canonical genetic code in green algae

Background  

A non-canonical nuclear genetic code, in which TAG and TAA have been reassigned from stop codons to glutamine, has evolved independently in several eukaryotic lineages, including the ulvophycean green algal orders Dasycladales and Cladophorales. To study the phylogenetic distribution of the standard and non-canonical genetic codes, we generated sequence data of a representative set of ulvophycean green algae and used a robust green algal phylogeny to evaluate different evolutionary scenarios that may account for the origin of the non-canonical code.     

Three decades of listeriology through the prism of technological advances

Decades of breakthroughs resulting from cross feeding of microbiological research and technological innovation have promoted Listeria monocytogenes to the rank of model microorganism to study host–pathogen interactions. The extraordinary capacity of this bacterium to interfere with a vast array of host cellular processes uncovered new concepts in microbiology, cell biology and infection biology. Here, we review technological advances that revealed how bacteria and host interact in space and time at the molecular, cellular, tissue and whole body scales, ultimately revolutionising our understanding of Listeria pathogenesis. With the current bloom of multidisciplinary integrative approaches, Listeria entered a new microbiology era.