1.Rewiring the Pneumococcal Cell Cycle with Serine/Threonine- and Tyrosine-kinases.
Grangeasse C Trends Microbiol. 2016 Sep;24(9):713-724. doi: 10.1016/j.tim.2016.04.004. Epub 2016 Apr 26.
Over the past decade, Streptococcus pneumoniae (the pneumococcus) has gained prominence as a model for studying the bacterial cell cycle. This important human pathogen possesses a characteristic diplo-ovococcal cell shape and produces a protective polysaccharide capsule required for virulence, and it has been used to investigate natural genetic transformation. Recent advances have demonstrated that the pneumococcus has evolved phosphorylation-dependent regulatory mechanisms dedicated to controlling cell division and ensuring the concealment of the newborn cells by the capsule. In this review, I survey the role of the only two serine/threonine- (StkP) and tyrosine-kinases (CpsD) of the pneumococcus and discuss the existence of interconnected phosphorylation networks coordinating cell division and morphogenesis with key aspects of the cell cycle.
2.Tyrosine-1 and threonine-4 phosphorylation marks complete the RNA polymerase II CTD phospho-code.
Heidemann M;Eick D RNA Biol. 2012 Sep;9(9):1144-6. doi: 10.4161/rna.21726. Epub 2012 Sep 1.
Eukaryotic RNA polymerase II (RNAP II) has evolved an array of heptad repeats with the consensus sequence Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7 at the carboxy-terminal domain (CTD) of its largest subunit (Rpb1). Dynamic phosphorylation of Ser2, Ser5 and Ser7 residues orchestrates the binding of transcription and RNA processing factors to the transcription machinery. Recent studies show that the two remaining potential phosphorylation sites, tyrosine-1 and threonine-4, are phosphorylated as well and contribute to the previously proposed "CTD code". With the impairment of binding of CTD interacting factors, these novel phosphorylation marks add an accessory layer of regulation to the RNAP II transcription cycle.
3.Alterations in lens protein tyrosine phosphorylation and phosphatidylinositol 3-kinase signaling during selenite cataract formation.
Chandrasekher G;Sailaja D Curr Eye Res. 2004 Feb;28(2):135-44.
PURPOSE: ;Protein tyrosine phosphorylation is an important event in the cell signal transduction process. Phosphatidylinositol-3 kinase (PI-3K) is an intracellular signal mediator and plays a key role in many cellular functions. In this study we have examined the changes in lens protein tyrosine phosphorylation and its impact on phosphatidylinositol 3-kinase (PI-3K) signaling during selenite cataract development.;METHODS: ;Cataract was induced in 10 days old rat pups by a single sub-cutaneous injection of sodium selenite (30 microM/Kg body weight) and lenses were collected at different stages of cataract development. Immunoprecipitation and Western immunoblotting were employed to determine protein tyrosine phosphorylation, PI-3K activity and protein in lens cell extracts. Tyrosine kinase activity in lens membrane preparations was assayed in the presence of a synthetic substrate peptide and [32P]ATP.;RESULTS: ;Protein tyrosine phosphorylation in the lens was disrupted before the onset of cataract. A decrease in tyrosine phosphorylation of lens proteins was observed within 2-3 days of selenite injection (pre-cataract stage). The effect was much more prominent with the progression of cataract.
