SUMMARY It has been suspected that cell cycle progression might be functionally coupled with RNA processing. However, little is known about the role of the precise splicing control in cell cycle progression. Here, we report that SON, a large Ser/Arg (SR)-related protein, is a splicing co-factor contributing to efficient splicing of cell cycle regulators. Down-regulation of SON leads to severe impairment of spindle pole separation, microtubule dynamics, and genome integrity. These molecular defects result from inadequate RNA splicing of a specific set of cell cycle-related genes that possess weak splice sites. Furthermore, we show that SON facilitates the interaction of SR proteins with RNA polymerase II and other key spliceosome components, suggesting its function in efficient co-transcriptional RNA processing. These results reveal a mechanism for controlling cell cycle progression through SON-dependent constitutive splicing at suboptimal splice sites, with strong implications for its role in cancer and other human diseases.

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Individuals with CKD are particularly predisposed to thrombosis after vascular injury. Using mouse models, we recently described indoxyl sulfate, a tryptophan metabolite retained in CKD and an activator of tissue factor (TF) through aryl hydrocarbon receptor (AHR) signaling, as an inducer of thrombosis across the CKD spectrum. However, the translation of findings from animal models to humans is often challenging. Here, we investigated the uremic solute-AHR-TF thrombosis axis in two human cohorts, using a targeted metabolomics approach to probe a set of tryptophan products and high-throughput assays to measure AHR and TF activity. Analysis of baseline serum samples was performed from 473 participants with advanced CKD from the Dialysis Access Consortium Clopidogrel Prevention of Early AV Fistula Thrombosis trial. Participants with subsequent arteriovenous thrombosis had significantly higher levels of indoxyl sulfate and kynurenine, another uremic solute, and greater activity of AHR and TF, than those without thrombosis. Pattern recognition analysis using the components of the thrombosis axis facilitated clustering of the thrombotic and nonthrombotic groups. We further validated these findings using 377 baseline samples from participants in the Thrombolysis in Myocardial Infarction II trial, many of whom had CKD stage 2-3. Mechanistic probing revealed that kynurenine enhances thrombosis after vascular injury in an animal model and regulates thrombosis in an AHR-dependent manner. This human validation of the solute-AHR-TF axis supports further studies probing its utility in risk stratification of patients with CKD and exploring its role in other diseases with heightened risk of thrombosis.

Fusion protein AML1-ETO, resulting from t(8;21) translocation, is highly related to leukemia development. It has been reported that full-length AML1-ETO blocks AML1 function and requires additional mutagenic events to promote leukemia. We have previously shown that the expression of AE9a, a splice isoform of AML1-ETO, can rapidly cause leukemia in mice. To understand how AML1-ETO is involved in leukemia development, we took advantage of our AE9a leukemia model and sought to identify its interacting proteins from primary leukemic cells. Here, we report the discovery of a novel AE9a binding partner PRMT1 (protein arginine methyltransferase 1). PRMT1 not only interacts with but also weakly methylates arginine 142 of AE9a. Knockdown of PRMT1 affects expression of a specific group of AE9a-activated genes. We also show that AE9a recruits PRMT1 to promoters of AE9a-activated genes, resulting in enrichment of H4 arginine 3 methylation, H3 Lys9/14 acetylation, and transcription activation. More importantly, knockdown of PRMT1 suppresses the self-renewal capability of AE9a, suggesting a potential role of PRMT1 in regulating leukemia development. (Blood. 2012;119(21):4953-4962) IntroductionAcute myeloid leukemia (AML) is closely associated with chromosomal abnormalities. 1 The AML1 gene (also known as CBFA2, PEBP2␣B, and RUNX1) was initially identified as a target of chromosomal translocation in t(8;21), which is associated with 15% of de novo AML cases and Յ 40% in the AML subtype M2 of the French-American-British classification. 2,3 This specific translocation at t(8;21) involves the AML1 gene on chromosome 21 and the ETO (also known as MTG8) gene on chromosome 8 and generates an AML1-ETO fusion transcription factor. 4 AML1-ETO inherits the DNA binding RUNT domain from AML1 and is functionally characterized as a transcription factor for both gene repression and activation. 3,[5][6][7] It has been shown that AML1-ETO negatively regulates AML1 target genes, possibly through interaction with corepressor proteins such as mSin3A, N-CoR/SMRT (nuclear receptor corepressor/silencing mediator for retinoic acid receptor and thyroid hormone receptor), and HDACs (histone deacetylases). [8][9][10] AML1-ETO could also act as a transactivator on certain genes. One of the possible mechanisms is by recruiting histone modifiers to make chromatin structure more accessible to the transcription activation machinery, resulting in gene activation. A recent finding shows that p300 binds to NHR1 domain of AML1-ETO to facilitate transcription. 11 A variety of posttranslational modifications, including acetylation, methylation, and phosphorylation, on specific residues of histones and their corresponding enzymes has been discovered. 12 It is well documented that a specific histone modification on a promoter could determine the state of transcription. Specifically, methylation on histone H4 arginine 3 (Arg3) by PRMT1 (protein arginine methyltransferase 1) generally correlates with transcription activation. 13 PRMT1 is the most predominant arginine ...

Our data show that the brainstem as well as more rostral regions are involved in voluntary urine storage and these regions are functionally separated from those associated with bladder cold perception in healthy individuals.

Chronic kidney disease (CKD/uremia) remains vexing because it increases the risk of atherothrombosis and is also associated with bleeding complications on standard antithrombotic/antiplatelet therapies. Although the associations of indolic uremic solutes and vascular wall proteins [such as tissue factor (TF) and aryl hydrocarbon receptor (AHR)] are being defined, the specific mechanisms that drive the thrombotic and bleeding risks are not fully understood. We now present an indolic solute–specific animal model, which focuses on solute-protein interactions and shows that indolic solutes mediate the hyperthrombotic phenotype across all CKD stages in an AHR- and TF-dependent manner. We further demonstrate that AHR regulates TF through STIP1 homology and U-box–containing protein 1 (STUB1). As a ubiquitin ligase, STUB1 dynamically interacts with and degrades TF through ubiquitination in the uremic milieu. TF regulation by STUB1 is supported in humans by an inverse relationship of STUB1 and TF expression and reduced STUB1-TF interaction in uremic vessels. Genetic or pharmacological manipulation of STUB1 in vascular smooth muscle cells inhibited thrombosis in flow loops. STUB1 perturbations reverted the uremic hyperthrombotic phenotype without prolonging the bleeding time, in contrast to heparin, the standard-of-care antithrombotic in CKD patients. Our work refines the thrombosis axis (STUB1 is a mediator of indolic solute–AHR-TF axis) and expands the understanding of the interconnected relationships driving the fragile thrombotic state in CKD. It also establishes a means of minimizing the uremic hyperthrombotic phenotype without altering the hemostatic balance, a long-sought-after combination in CKD patients.

Preoperative evaluation of DI is of benefit because it enhances predictive value of the PFS.