Hippo signaling pathway: A comprehensive gene expression profile analysis in breast cancer

Breast cancer (BC) is the most frequently diagnosed malignancy in women and a major public health concern. The Hippo pathway is an evolutionarily conserved signaling pathway that serves as a key regulator for a wide variety of biological processes. Hippo signaling has been shown to have both oncogenic and tumor-suppressive functions in various cancers. Core components of the Hippo pathway consist of various kinases and downstream effectors such as YAP/TAZ. In the current report, differential expression of Hippo pathway elements as well as the correlation of Hippo pathway mRNAs with various clinicopathologic characteristics, including molecular subtypes, receptor status, and methylation status, has been investigated in BC using METABRIC and TCGA datasets. In this review, we note deregulation of several Hippo signaling elements in BC patients. Moreover, we see examples of negative correlations between methylation of Hippo genes and mRNA expression. The expression of Hippo genes significantly varies between different receptor subgroups. Because of the clear associations between mRNA expression and methylation status, DNA methylation may be one of the mechanisms that regulate the Hippo pathway in BC cells. Differential expression of Hippo genes among various BC molecular subtypes suggests that Hippo signaling may function differently in different subtypes of BC. Our data also highlights an interesting link between Hippo components' transcription and ER negativity in BC. In conclusion, substantial deregulation of Hippo signaling components suggests an important role of these genes in breast cancer.

Comparison of the NMR and X-ray structures of the HIV-1 matrix protein: evidence for conformational changes during viral assembly

The three-dimensional solution- and solid-state structures of the human immunodeficiency virus type-1 (HIV-1) matrix protein have been determined recently in our laboratories by NMR and X-ray crystallographic methods (Massiah et al. 1994. J Mol Biol 244:198-223; Hill et al. 1996. Proc Natl Acad Sci USA 93:3099-3104). The matrix protein exists as a monomer in solution at low millimolar protein concentrations, but forms trimers in three different crystal lattices. Although the NMR and X-ray structures are similar, detailed comparisons have revealed an approximately 6 A displacement of a short 3(10) helix (Pro 66-Gly 71) located at the trimer interface. High quality electron density and nuclear Overhauser effect (NOE) data support the integrity of the X-ray and NMR models, respectively. Because matrix apparently associates with the viral membrane as a trimer, displacement of the 3(10) helix may reflect a physiologically relevant conformational change that occurs during virion assembly and disassembly. These findings further suggest that Pro 66 and Gly 71, which bracket the 3(10) helix, serve as "hinges" that allow the 3(10) helix to undergo this structural reorientation.

Crystal structures of the trimeric human immunodeficiency virus type 1 matrix protein: implications for membrane association and assembly

The human immunodeficiency virus type 1 (HIV-1) matrix protein forms a structural shell associated with the inner viral membrane and performs other essential functions throughout the viral life cycle. The crystal structure of the HIV-1 matrix protein, determined at 2.3 angstrom resolution, reveals that individual matrix molecules are composed of five major helices capped by a three-stranded mixed beta-sheet. Unexpectedly, the protein assembles into a trimer in three different crystal lattices, burying 1880 angstrom2 of accessible surface area at the trimer interfaces. Trimerization appears to create a large, bipartite membrane binding surface in which exposed basic residues could cooperate with the N-terminal myristoyl groups to anchor the protein on the acidic inner membrane of the virus.

Structure of the regulatory complex of Escherichia coli IIIGlc with glycerol kinase

The phosphocarrier protein IIIGlc is an integral component of the bacterial phosphotransferase (PTS) system. Unphosphorylated IIIGlc inhibits non-PTS carbohydrate transport systems by binding to diverse target proteins. The crystal structure at 2.6 A resolution of one of the targets, glycerol kinase (GK), in complex with unphosphorylated IIIGlc, glycerol, and adenosine diphosphate was determined. GK contains a region that is topologically identical to the adenosine triphosphate binding domains of hexokinase, the 70-kD heat shock cognate, and actin. IIIGlc binds far from the catalytic site of GK, indicating that long-range conformational changes mediate the inhibition of GK by IIIGlc. GK and IIIGlc are bound by hydrophobic and electrostatic interactions, with only one hydrogen bond involving an uncharged group. The phosphorylation site of IIIGlc, His90, is buried in a hydrophobic environment formed by the active site region of IIIGlc and a 3(10) helix of GK, suggesting that phosphorylation prevents IIIGlc binding to GK by directly disrupting protein-protein interactions.

Structure of the regulatory complex of Escherichia coli IIIGlc with glycerol kinase

The phosphocarrier protein IIIGlc is an integral component of the bacterial phosphotransferase (PTS) system. Unphosphorylated IIIGlc inhibits non-PTS carbohydrate transport systems by binding to diverse target proteins. The crystal structure at 2.6 A resolution of one of the targets, glycerol kinase (GK), in complex with unphosphorylated IIIGlc, glycerol, and adenosine diphosphate was determined. GK contains a region that is topologically identical to the adenosine triphosphate binding domains of hexokinase, the 70-kD heat shock cognate, and actin. IIIGlc binds far from the catalytic site of GK, indicating that long-range conformational changes mediate the inhibition of GK by IIIGlc. GK and IIIGlc are bound by hydrophobic and electrostatic interactions, with only one hydrogen bond involving an uncharged group. The phosphorylation site of IIIGlc, His90, is buried in a hydrophobic environment formed by the active site region of IIIGlc and a 3(10) helix of GK, suggesting that phosphorylation prevents IIIGlc binding to GK by directly disrupting protein-protein interactions.

Three-dimensional structure of the Escherichia coli phosphocarrier protein IIIglc

The crystal structure of a proteolytically modified form of the Escherichia coli phosphocarrier and signal transducing protein IIIglc has been determined by multiple isomorphous and molecular replacement. The model has been refined to an R-factor of 0.166 for data between 6- and 2.1-A resolution with an rms deviation of 0.020 A from ideal bond lengths and 3.2 degrees from ideal bond angles. The molecule is a beta-sheet sandwich, with six antiparallel strands on either side. Several short distorted helices line the periphery of the active site, which is a shallow extremely hydrophobic depression approximately 18 A in diameter near the center of one face. The side chains of the active site histidine residues 75 and 90 face each other at the center of the depression, with the N3 positions exposed to solvent, separated by 3.3 A in an excellent position to form adducts with phosphate. Chloroplatinate forms a divalent adduct with both histidyl side chains, suggesting that the phosphodonor reaction might proceed through a similar transition state. The hydrophobic patch forms the primary crystal contact, suggesting a mode of association of IIIglc with other components of the phosphoenolpyruvate-dependent phosphotransferase system.