Transcriptional Regulation of Tyrosine Phenol-lyase Gene Mediated through TyrR and cAMP Receptor Protein

Using a lac reporter system in Escherichia coli, we showed that the expression of E. herbicola tpl was regulated through TyrR and cAMP receptor protein. Three TyrR boxes upstream of tpl were essential for full expression. The results suggested that the tyrosine-mediated TyrR hexamerization was an important process. The DNA bending between two TyrR boxes, which is triggered by the binding of cAMP receptor protein, may facilitate the conformational change of TyrRs.     

Transcriptional regulation of a herpes simplex virus immediate early gene is mediated through an enhancer-type sequence

An enhancer-type sequence has been identified in the promoter region for the herpes simplex virus type 1 (HSV-1) immediate early (IE) mRNA 3. The enhancer-type activity is host cell dependent, being greater in human cells and Syrian hamster cells (the usual host cell for in vitro propagation of HSV) than in Chinese hamster or mouse cells. Enhancer activity is stimulated up to 10-fold after superinfection by tsK, a temperature-sensitive mutant of HSV-1. The induction of enhancer activity is independent of de novo protein synthesis, showing that trans-activation is effected by a component of the virion. We propose that trans-regulation of IE mRNA 3 is mediated through an enhancer-type sequence, and that this provides one explanation for previously described regulation of HSV IE mRNAs by virion components.     

Transcriptional regulation of the human TATA binding protein gene

The human TATA binding protein (TBP) locus consists of a functional domain of three closely linkedhousekeeping genes (TBP, PSMB1 (proteasomal C5 subunit), and PDCD2 (programmed cell death-2)) within a 50-kb interval at chromosome position 6q27. Here we demonstrate that a genomic clone spanning the 20-kb TBP gene, with 12 kb 5' and 3' flanking sequences, was fully functional in stable, transfected L-cells harboring a single copy of this transgene, including after long-term (60 day) culture in the absence of drug selective pressure. Furthermore, we were only able to detect DNaseI hypersensitive sites at the TBP and PSMB1 promoters present within this 44-kb fragment. Our data suggest that this 44-kb genomic region possesses genetic regulatory elements that not only drive ubiquitous expression of TBP but also negate chromatin and DNA methylation induced silencing, which is normally associated with transgenes stably integrated into tissue culture cells.     

Redox regulation of protein tyrosine phosphatases during receptor tyrosine kinase signal transduction

In addition to protein phosphorylation, redox-dependent post-translational modification of proteins is emerging as a key signaling system that has been conserved throughout evolution and that influences many aspects of cellular homeostasis. Both systems exemplify dynamic regulation of protein function by reversible modification, which, in turn, regulates many cellular processes such as cell proliferation, differentiation and apoptosis. In this article we focus on the interplay between phosphorylation- and redox-dependent signaling at the level of phosphotyrosine phosphatase-mediated regulation of receptor tyrosine kinases (RTKs). We propose that signal transduction by oxygen species through reversible phosphotyrosine phosphatase inhibition, represents a widespread and conserved component of the biochemical machinery that is triggered by RTKs.     

Crystallization and crystal data on tyrosine phenol-lyase

Crystals of the apoenzyme of tyrosine phenol-lyase (EC 4.1.99.2), a pyridoxal 5'-phosphate-dependent enzyme from Citrobacter intermedius, have been grown by vapor diffusion of an ammonium sulfate solution to a protein solution. The crystals belong to space group P2(1)2(1)2, with dimensions of a = 75.5 A, b = 138.4 A and c = 94.1 A and diffract up to 2.7 A resolution. The asymmetric unit contains one half of the enzyme tetrameric molecule. Two heavy-atom derivatives of the crystals have been obtained.