Elucidating mechanisms of genetic cross-disease associations at the PROCR vascular disease locus

Many individual genetic risk loci have been associated with multiple common human diseases. However, the molecular basis of this pleiotropy often remains unclear. We present an integrative approach to reveal the molecular mechanism underlying the PROCR locus, associated with lower coronary artery disease (CAD) risk but higher venous thromboembolism (VTE) risk. We identify PROCR-p.Ser219Gly as the likely causal variant at the locus and protein C as a causal factor. Using genetic analyses, human recall-by-genotype and in vitro experimentation, we demonstrate that PROCR-219Gly increases plasma levels of (activated) protein C through endothelial protein C receptor (EPCR) ectodomain shedding in endothelial cells, attenuating leukocyte– endothelial cell adhesion and vascular inflammation. We also associate PROCR-219Gly with an increased pro- thrombotic state via coagulation factor VII, a ligand of EPCR. Our study, which links PROCR-219Gly to CAD through anti-inflammatory mechanisms and to VTE through pro-thrombotic mechanisms, provides a framework to reveal the mechanisms underlying similar cross-phenotype associations

The Tetrahymena telomerase p75–p45–p19 subcomplex is a unique CST complex

Tetrahymena telomerase holoenzyme subunits p75, p45 and p19 form a subcomplex (7–4–1) peripheral to the catalytic core. We report structures of p45 and p19 and reveal them as the Stn1 and Ten1 subunits of the CST complex, which stimulates telomerase complementary-strand synthesis. 7–4–1 binds telomeric single-stranded DNA, and mutant p19 overexpression causes telomere 3′-overhang elongation. We propose that telomerase-tethered Tetrahymena CST coordinates telomere G-strand and C-strand synthesis

Analyses of Candida Cdc13 Orthologues Revealed a Novel OB Fold Dimer Arrangement, Dimerization-Assisted DNA Binding, and Substantial Structural Differences between Cdc13 and RPA70

The budding yeast Cdc13-Stn1-Ten1 complex is crucial for telomere protection and has been proposed to resemble the RPA complex structurally and functionally. The Cdc13 homologues in Candida species are unusually small and lack two conserved domains previously implicated in telomere regulation, thus raising interesting questions concerning the mechanisms and evolution of these proteins. In this report, we show that the unusually small Cdc13 homologue in Candida albicans is indeed a regulator of telomere lengths and that it associates with telomere DNA in vivo. We demonstrated high-affinity telomere DNA binding by C. tropicalis Cdc13 (CtCdc13) and found that dimerization of this protein through its OB4 domain is important for high-affinity DNA binding. Interestingly, CtCdc13-DNA complex formation appears to involve primarily recognition of multiple copies of a six-nucleotide element (GGATGT) that is shared by many Candida telomere repeats. We also determined the crystal structure of the OB4 domain of C. glabrata Cdc13, which revealed a novel mechanism of OB fold dimerization. The structure also exhibits marked differences to the C-terminal OB fold of RPA70, thus arguing against a close evolutionary kinship between these two proteins. Our findings provide new insights on the mechanisms and evolution of a critical telomere end binding protein