Drosophila homeotic genes encode transcription factors thought to control segmental identity by regulating expression of largely unknown target genes. The formation of the second midgut constriction requires the Ultrabithorax (Ubx) and abdominal-A (abd-A) homeotic genes and decapentaplegic (dpp), a gene encoding a member of the TGF beta family of proteins. We identified a 674 bp enhancer of dpp controlling its expression in the second constriction domain of the visceral mesoderm (parasegment 7). Normal enhancer function requires positive regulation by Ubx and negative regulation by abd-A. This enhancer contains UBX- and ABD-A-binding sites defined in vitro. By generating complementary alterations of the binding sites and the binding specificity of UBX, we show that Ubx directly regulates dpp expression. These regulatory interactions are relevant to normal development, because a transgene made with this enhancer driving a dpp transcription unit rescues the second midgut constriction and larval lethality phenotypes of dpps mutations.

Animals↗

PubMed1994

Catalytic and ligand binding properties of the FK506 binding protein FKBP12: effects of the single amino acid substitution of Tyr82 to Leu.

The binding of FK506 and rapamycin to their cytosolic receptor FKBP12 is an intermediate step in the paths leading to their potent immunosuppressive properties. One of the amino acids defining the hydrophobic binding cleft for the macrocycles is Tyr82, which is thought to form a hydrogen bond with the amide oxygens of the common pipecolyl structural element within the two macrolides. To understand better the influence of this amino acid residue in catalytic activity (cis-trans peptidyl prolyl isomerization) and ligand binding properties, a Tyr82 to Leu site-specific modification of FKBP12 was prepared, purified and characterized. Kinetic experiments have demonstrated that the Tyr82 to Leu modification has a greater effect on catalytic properties than on ligand binding affinities, a result which indicates that these inhibitors may not be binding as true transition-state analogues. In an additional test for cellular function, expression of both wild-type and mutant human FKBP12 in a strain of Saccharomyces cerevisiae rendered resistant to rapamycin by deletion of the gene encoding a cytosolic rapamycin binding protein (RPB1), the yeast homologue of FKBP12, restored wild-type drug sensitivity.

Base Sequence↗

PubMed1994

Epristeride is a selective and specific uncompetitive inhibitor of human steroid 5 alpha-reductase isoform 2.

Specificity of an enzyme inhibitor can have profound implications upon the compound's therapeutic potential, utility and safety profile. As potent inhibitors of human steroid 5 alpha-reductase (SR) the 3-androstene-3-carboxylic acids, or steroidal acrylates, may be useful in treatment of diseases such as benign prostatic hyperplasia for which 5 alpha-dihydrotestosterone (DHT) appears to be a causative agent. To determine its specificity profile, the interactions of a representative compound from this class, N-(t-butyl)androst-3,5-diene-17 beta-carboxamide-3-carboxylic acid (epristeride, SK&F 105657), have been studied with 7 other steroid processing enzymes and 5 steroid hormone receptors. The affinity of epristeride for each of these 12 potential targets was found to be at least 1000-fold weaker than that for SR, the intended target. In addition, using samples of the individually expressed two known forms of human SRs, epristeride has been shown to be a selective inhibitor of the recombinant human SR type 2, the predominant activity found in the prostate of man. Nonetheless, the mechanisms of SR inhibition for both isoenzymes involve formation of a ternary complex with epristeride, NADP+, and enzyme. Epristeride, consequently, has been shown to be an uncompetitive inhibitor versus steroid substrate of both human SR isoenzymes. These results suggest that this 3-androstene-3-carboxylic acid is a specific and selective inhibitor of the human type 2 SR, and that epristeride is an attractive compound for further investigation as a safe and effective therapeutic agent in the potential treatment of disease states associated with DHT-induced tissue growth.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed1994

Clinical practice guidelines and critical paths--roadmaps to quality, cost-effective care (Part I).

Clinical practice guidelines and critical paths have gained widespread acceptance in recent years. Part I of this article will examine clinical practice guidelines, or practice parameters, and their application to patient care. Part II (in the February issue of JAHIMA) will look at multi-disciplinary care plans known as critical paths and how they can incorporate clinical practice guidelines. Health information management professionals can play an important role in implementation and ongoing evaluation of these clinical tools.

Clinical Protocols↗

PubMed1994