Systematic proteomics of endogenous human cohesin reveals an interaction with diverse splicing factors and RNA-binding proteins required for mitotic progression.

The cohesin complex regulates sister chromatid cohesion, chromosome organization, gene expression, and DNA repair. Cohesin is a ring complex composed of four core subunits and seven regulatory subunits. In an effort to comprehensively identify additional cohesin-interacting proteins, we used gene editing to introduce a dual epitope tag into the endogenous allele of each of 11 known components of cohesin in cultured human cells, and we performed MS analyses on dual-affinity purifications. In addition to reciprocally identifying all known components of cohesin, we found that cohesin interacts with a panoply of splicing factors and RNA-binding proteins (RBPs). These included diverse components of the U4/U6.U5 tri-small nuclear ribonucleoprotein complex and several splicing factors that are commonly mutated in cancer. The interaction between cohesin and splicing factors/RBPs was RNA- and DNA-independent, occurred in chromatin, was enhanced during mitosis, and required RAD21. Furthermore, cohesin-interacting splicing factors and RBPs followed the cohesin cycle and prophase pathway of cell cycle-regulated interactions with chromatin. Depletion of cohesin-interacting splicing factors and RBPs resulted in aberrant mitotic progression. These results provide a comprehensive view of the endogenous human cohesin interactome and identify splicing factors and RBPs as functionally significant cohesin-interacting proteins.

The genomic landscape of the Ewing Sarcoma family of tumors reveals recurrent STAG2 mutation.

The Ewing sarcoma family of tumors (EFT) is a group of highly malignant small round blue cell tumors occurring in children and young adults. We report here the largest genomic survey to date of 101 EFT (65 tumors and 36 cell lines). Using a combination of whole genome sequencing and targeted sequencing approaches, we discover that EFT has a very low mutational burden (0.15 mutations/Mb) but frequent deleterious mutations in the cohesin complex subunit STAG2 (21.5% tumors, 44.4% cell lines), homozygous deletion of CDKN2A (13.8% and 50%) and mutations of TP53 (6.2% and 71.9%). We additionally note an increased prevalence of the BRCA2 K3326X polymorphism in EFT patient samples (7.3%) compared to population data (OR 7.1, p = 0.006). Using whole transcriptome sequencing, we find that 11% of tumors pathologically diagnosed as EFT lack a typical EWSR1 fusion oncogene and that these tumors do not have a characteristic Ewing sarcoma gene expression signature. We identify samples harboring novel fusion genes including FUS-NCATc2 and CIC-FOXO4 that may represent distinct small round blue cell tumor variants. In an independent EFT tissue microarray cohort, we show that STAG2 loss as detected by immunohistochemistry may be associated with more advanced disease (p = 0.15) and a modest decrease in overall survival (p = 0.10). These results significantly advance our understanding of the genomic and molecular underpinnings of Ewing sarcoma and provide a foundation towards further efforts to improve diagnosis, prognosis, and precision therapeutics testing.

Frequent truncating mutations of STAG2 in bladder cancer.

Here we report the discovery of truncating mutations of the gene encoding the cohesin subunit STAG2, which regulates sister chromatid cohesion and segregation, in 36% of papillary non-invasive urothelial carcinomas and 16% of invasive urothelial carcinomas of the bladder. Our studies suggest that STAG2 has a role in controlling chromosome number but not the proliferation of bladder cancer cells. These findings identify STAG2 as one of the most commonly mutated genes in bladder cancer.

Evaluation of electrocardiographic algorithms in the assessment of the infarct-related artery in acute myocardial infarction.

OBJECTIVES: In acute myocardial infarction, it is of great value to identify the infarct-related artery and the site of occlusion in a coronary artery (proximal versus distal). This study assessed the diagnostic value of two previously published electrocardiographic algorithms to identify the infarct-related artery and the site of occlusion in anterior and inferior acute myocardial infarction. METHODS AND RESULTS: We studied retrospectively a group of 88 patients with a first myocardial infarction. We determined the infarct-related artery using the electrocardiographic algorithms on the electrocardiogram at the time of admission and compared these results with the angiographically determined infarct-related artery. The best electrocardiographic algorithm could determine the infarct-related artery in an inferior myocardial infarction as the left circumflex coronary artery and as the proximal and distal right coronary artery with a sensitivity of 63%, 67% and 80%, respectively, and a specificity of 100%, 82% and 69%, respectively. One algorithm was unable to diagnose a left circumflex coronary artery occlusion. In an anterior myocardial infarction the best electrocardiographic algorithm could determine the infarct-related artery as the proximal and distal left anterior descending coronary artery with a sensitivity of 85% and 80%, respectively, and with a specificity of 77% and 82%, respectively. CONCLUSION: In acute myocardial infarction the use of electrocardiographic algorithms is helpful to predict the site of occlusion and can play a crucial role in the care of patients.