University of Texas System

About: University of Texas System is a education organization based out in Austin, Texas, United States. It is known for research contribution in the topics: Cancer & Population. The organization has 13901 authors who have published 10925 publications receiving 319328 citations. The organization is also known as: UT System.

Toxin Synthesis by Clostridium difficile Is Regulated through Quorum Signaling

Abstract: Clostridium difficile infection (CDI) is dramatically increasing as a cause of antibiotic- and hospital-associated diarrhea worldwide. C. difficile, a multidrug-resistant pathogen, flourishes in the colon after the gut microbiota has been altered by antibiotic therapy. Consequently, it produces toxins A and B that directly cause disease. Despite the enormous public health problem posed by this pathogen, the molecular mechanisms that regulate production of the toxins, which are directly responsible for disease, remained largely unknown until now. Here, we show that C. difficile toxin synthesis is regulated by an accessory gene regulator quorum-signaling system, which is mediated through a small ( IMPORTANCE Clostridium difficile infection (CDI) is the most common definable cause of hospital-acquired and antibiotic-associated diarrhea in the United States, with the total cost of treatment estimated between 1 and 4.8 billion U.S. dollars annually. C. difficile, a Gram-positive, spore-forming anaerobe, flourishes in the colon after the gut microbiota has been altered by antibiotic therapy. As a result, there is an urgent need for non-antibiotic CDI treatments that preserve the colonic microbiota. C. difficile produces toxins A and B, which are directly responsible for disease. Here, we report that C. difficile regulates its toxin synthesis by quorum signaling, in which a novel signaling peptide activates transcription of the disease-causing toxin genes. This finding provides new therapeutic targets to be harnessed for novel nonantibiotic therapy for C. difficile infections.

Generalized approach to the regulation and integration of gene expression.

Abstract: The volume of electron flow through the cbb3 branch of the electron transport chain and the redox state of the quinone pool generate signals that regulate photosynthesis gene expression in Rhodobacter sphaeroides. An inhibitory signal is generated at the level of the catalytic subunit of the cbb3 cytochrome c oxidase and is transduced through the membrane-localized PrrC polypeptide to the PrrBA two-component activation system, which controls the expression of most of the photosynthesis genes in response to O2. The redox state of the quinone pool is monitored by the redox-active AppA antirepressor protein, which determines the functional state of the PpsR repressor protein. The antirepressor/repressor system as well as a modulator of AppA function, TspO, together with FnrL and PrrA stringently control photopigment gene expression. These regulatory elements, together with spectral complex-specific assembly factors, control the ultimate cellular levels and composition of the photosynthetic membrane.

Breast cancer brain metastases.

Abstract: Breast cancer is the most common malignancy in woman in the USA. Metastasis is a major cause of morbidity and mortality in breast cancer patients. Total incidence of brain metastases of breast cancer is about 30%. Because of the improvements in control of systemic disease, for example the successful use of Trastuzumab, and the consequent prolonged life span, the incidence of brain metastases is increasing in breast cancer patients. The progressive neurological disabilities not only impair the quality of life, but also decrease the survival in patients. However, current treatments are of limited effectiveness. This is partially caused by the unique structure of the blood brain barrier. So far very little is known about the mechanisms how breast cancer metastizes to the brain. Some studies showed that ErbB2 overexpression is associated with the brain metastatic phenotype. Other molecules, like vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs) and chemokine receptor CXCR4 are also involved in the metastasis of breast cancer cell to the brain. The current review will briefly overview the clinical features of brain metastasis of breast cancer and discusses the relationship of blood brain barrier and ErbB2 signal pathway to brain metastasis in breast cancer.

Particulate Tyrosinase of Human Malignant Melanoma

Abstract: Studies of mammalian tyrosinase have been conducted principally with soluble forms (T1 faster, T2 slower migrating by gel electrophoresis). However, a majority of tyrosinase from mouse and human melanoma tissue is of a particulate (T3) nature, being bound to melanosomes. In addition, T1 and T2 enzymes have been considered isozymes with T3 being a separate enzyme. Using human malignant melanoma tissue, solubilization and purification of particulate tyrosinase have been attempted. Melanosome-bound tyrosinase was solubilized with sodium cholate and purified 1500-fold by ammonium sulfate fractionation, DEAE-cellulose column chromatography, concanavalin A affinity chromatography, and Sephadex G-150 gel filtration. Tryptic cleavage of this solubilized tyrosinase yielded a fast migrating tyrosinase by gel electrophoresis. This trypsin-cleaved tyrosinase was purified by Sephadex G-150 and DEAE-cellulose columns with an apparent final yield of 56% and an approximate 10000-fold purification. This preparation gave a single band by 7% gel electrophoresis and 5% sodium dodecyl sulfate gel electrophoresis. In addition, electrophoresis indicated that this tyrosinase was a glycoprotein showing positive staining by periodic acid/Schiff stain. This enzyme oxidized both l-tyrosine and l-3,4-dihydroxyphenylalanine at a similar rate. The molecular weight was approximated at 66 700 by sodium dodecyl sulfate gel electrophoresis. This enzyme migrated to the T1 position by gel electrophoresis; however, upon treatment with neuraminidase, it shifted to the T2 position. Sialic acid content was determined as 4.8%. Copper content was estimated as 2 atoms/molecule. These results tend to support the dynamic conversion of T3 T1 T2 rather than their existence as separate enzymes.