Mapping and functional characterization of the murine Smoothelin-like 1 promoter

BACKGROUND: Smoothelin-like 1 (SMTNL1, also known as CHASM) plays a role in promoting relaxation as well as adaptive responses to exercise, pregnancy and sexual development in smooth and skeletal muscle. Investigations of Smtnl1 transcriptional regulation are still lacking. Thus, in this study, we identify and characterize key regulatory elements of the mouse Smtnl1 gene. RESULTS: We mapped the key regulatory elements of the Smtnl1 promoter region: the transcriptional start site (TSS) lays -44 bp from the translational start codon and a TATA-box motif at -75 bp was conserved amongst all mammalian Smtnl1 promoters investigated. The Smtnl1 proximal promoter enhances expression up to 8-fold in smooth muscle cells and a second activating region lays 500 bp further upstream. Two repressing motifs were present (-118 to -218 bp and -1637 to -1869 bp). The proximal promoter is highly conserved in mammals and contains a mirror repeat sequence. In silico analysis suggests many transcription factors (notably MyoD) could potentially bind within the Smtnl1 proximal promoter sequence. CONCLUSION: Smtnl1 transcript was identified in all smooth muscle tissues examined to date, albeit at much lower levels than found in skeletal muscle. It is unlikely that multiple SMTNL1 isoforms exist since a single Smtnl1 transcription start site was identified in both skeletal and intestinal smooth muscle. Promoter studies suggest restrictive control of Smtnl1 expression in non-muscle cells

Determining crystal structures through crowdsourcing and coursework

We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality

Modulation of smooth muscle contractility by CHASM, a novel member of the smoothelin family of proteins

AbstractCyclic nucleotides acting through their associated protein kinases, the cGMP- and cAMP-dependent protein kinases, can relax smooth muscles without a change in free intracellular calcium concentration ([Ca2+]i), a phenomenon referred to as Ca2+ desensitization. The molecular mechanisms by which these kinases bring about Ca2+ desensitization are unknown and an understanding of this phenomenon may lead to better therapies for treating diseases involving defects in the contractile response of smooth muscles such as hypertension, bronchospasm, sexual dysfunction, gastrointestinal disorders and glaucoma. Utilizing a combination of real-time proteomics and smooth muscle physiology, we characterized a distinct subset of protein targets for cGMP-dependent protein kinase in smooth muscle. Among those phosphoproteins identified was calponin homology-associated smooth muscle (CHASM), a novel protein that contains a calponin homology domain and shares sequence similarity with the smoothelin family of smooth muscle specific proteins. Recombinant CHASM was found to evoke relaxation in a concentration dependent manner when added to permeabilized smooth muscle. A co-sedimentation assay with actin demonstrated that CHASM does not possess actin binding activity. Our findings indicate that CHASM is a novel member of the smoothelin protein family that elicits Ca2+ desensitization in smooth muscle

Risk Factors for Mortality in Patients with Alcoholic Hepatitis and Assessment of Prognostic Models: A Population-Based Study

BACKGROUND: Severe alcoholic hepatitis (AH) is associated with a substantial risk for short-term mortality