␤-arrestins are cytosolic proteins that form complexes with seventransmembrane receptors after agonist stimulation and phosphorylation by the G protein-coupled receptor kinases. They play an essential role in receptor desensitization and endocytosis, and they also serve as receptor-regulated signaling scaffolds and adaptors. Moreover, in the past decade, a growing list of protein-protein interactions of ␤-arrestins pertinent to these functions has been documented. The discovery of several novel functions of ␤-arrestins stimulated us to perform a global proteomics analysis of ␤-arrestininteracting proteins (interactome) as modulated by a model seventransmembrane receptor, the angiotensin II type 1a receptor, in an attempt to assess the full range of functions of these versatile molecules. As determined by LC tandem MS, 71 proteins interacted with ␤-arrestin 1, 164 interacted with ␤-arrestin 2, and 102 interacted with both ␤-arrestins. Some proteins bound only after agonist stimulation, whereas others dissociated. Bioinformatics analysis of the data indicates that proteins involved in cellular signaling, organization, and nucleic acid binding are the most highly represented in the ␤-arrestin interactome. Surprisingly, both S-arrestin (visual arrestin) and X-arrestin (cone arrestin) were also found in heteromeric complex with ␤-arrestins. The ␤-arrestin interactors distribute not only in the cytoplasm, but also in the nucleus as well as other subcellular compartments. The binding of 16 randomly selected newly identified ␤-arrestin partners was validated by coimmunoprecipitation assays in HEK293 cells. This study provides a comprehensive analysis of proteins that bind ␤-arrestin isoforms and underscores their potentially broad regulatory roles in mammalian cellular physiology. mass spectrometry ͉ seven-transmembrane receptor ͉ angiotensin II type 1a receptor ͉ interactome ͉ signal transduction S even-transmembrane receptors (7TMRs), the largest group of plasma membrane receptors, classically signal via activation of heterotrimeric G proteins and generation of second messengers such as cAMP, DAG, and IP3. Their signaling is rapidly quenched by a universal mechanism involving two families of proteins. G protein-coupled receptor kinases phosphorylate activated receptors, thereby promoting the binding of ␤-arrestin molecules (␤-arrestin 1 or 2, aka arrestin 2 and 3) or in the case of rhodopsin, visual arrestin (aka arrestin 1). The arrestin molecules ''desensitize'' the receptors by sterically inhibiting further G protein activation (1, 2).Over the past decade, however, a variety of additional functions of ␤-arrestins have been discovered. These include important roles in clathrin-mediated endocytosis of receptors and as signal transducers for a growing list of effector pathways such as MAP kinases, AKT, and phosphatidylinositol 3-kinase (PI3-kinase). Both the endocytic and signaling roles of ␤-arrestins rely on their ability to serve as adaptors and scaffolds that engage in regulated interactions with a variety of cell...

As a large family of RNA-binding proteins, pentatricopeptide repeat (PPR) proteins mediate multiple aspects of RNA metabolism in eukaryotes. Binding to their target single-stranded RNAs (ssRNAs) in a modular and base-specific fashion, PPR proteins can serve as designable modules for gene manipulation. However, the structural basis for nucleotide-specific recognition by designer PPR (dPPR) proteins remains to be elucidated. Here, we report four crystal structures of dPPR proteins in complex with their respective ssRNA targets. The dPPR repeats are assembled into a right-handed superhelical spiral shell that embraces the ssRNA. Interactions between different PPR codes and RNA bases are observed at the atomic level, revealing the molecular basis for the modular and specific recognition patterns of the RNA bases U, C, A and G. These structures not only provide insights into the functional study of PPR proteins but also open a path towards the potential design of synthetic sequence-specific RNA-binding proteins.

The RIG-I like receptors (RLRs) RIG-I and MDA5 are cytosolic RNA helicases best characterized as restriction factors for RNA viruses. However, evidence suggests RLRs participate in innate immune recognition of other pathogens, including DNA viruses. Kaposi’s sarcoma-associated herpesvirus (KSHV) is a human gammaherpesvirus and the etiological agent of Kaposi’s sarcoma and primary effusion lymphoma (PEL). Here, we demonstrate that RLRs restrict KSHV lytic reactivation and we demonstrate that restriction is facilitated by the recognition of host-derived RNAs. Misprocessed noncoding RNAs represent an abundant class of RIG-I substrates, and biochemical characterizations reveal that an infection-dependent reduction in the cellular triphosphatase DUSP11 results in an accumulation of select triphosphorylated noncoding RNAs, enabling their recognition by RIG-I. These findings reveal an intricate relationship between RNA processing and innate immunity, and demonstrate that an antiviral innate immune response can be elicited by the sensing of misprocessed cellular RNAs.

No abstract

Short interspersed nuclear elements (SINEs) are retrotransposons evolutionarily derived from endogenous RNA Polymerase III RNAs. Though SINE elements have undergone exaptation into gene regulatory elements, how transcribed SINE RNA impacts transcriptional and post-transcriptional regulation is largely unknown. This is partly due to a lack of information regarding which of the loci have transcriptional potential. Here, we present an approach (short interspersed nuclear element sequencing, SINE-seq), which selectively profiles RNA Polymerase III-derived SINE RNA, thereby identifying transcriptionally active SINE loci. Applying SINE-seq to monitor murine B2 SINE expression during a gammaherpesvirus infection revealed transcription from 28 270 SINE loci, with ∼50% of active SINE elements residing within annotated RNA Polymerase II loci. Furthermore, B2 RNA can form intermolecular RNA–RNA interactions with complementary mRNAs, leading to nuclear retention of the targeted mRNA via a mechanism involving p54nrb. These findings illuminate a pathway for the selective regulation of mRNA export during stress via retrotransposon activation.

The aim of this study was to determine the function of the NEAT1/miR-23a-3p/ SMC1A axis in cell proliferation and apoptosis in acute myeloid leukemia (AML).Microarray analysis was used to screen differentially expressed lncRNAs/miRNAs/ mRNAs in primary AML cells. The expression of nuclear paraspeckle assembly transcript 1 (NEAT1), miR-23a-3p, and structural maintenance of chromosome 1 alpha (SMC1A) in primary AML cells and THP-1 cells were measured by quantitative real-time polymerase chain reaction (qRT-PCR). A Cell Counting Kit-8 (CCK-8) assay was used to analyze proliferation. Cell cycle progression and apoptosis were examined by flow cytometry. RNA immunoprecipitation (RIP) and dual-luciferase assays were performed to determine the correlation between miR-23a-3p and NEAT1 or SMC1A. The qRT-PCR illustrated that NEAT1 and SMC1A expression was decreased but that miR-23a-3p expression was increased in primary AML cells and THP-1 cells compared with that in normal cells. The RIP assay and dual-luciferase assay revealed the targeting relationship between miR-23a-3p and NEAT1 or SMC1A. The CCK-8 assay showed that the overexpression of NEAT1 and SMC1A or repression of miR-23a-3p inhibited cell proliferation. Flow cytometry showed that the upregulation of NEAT1 and SMC1A or repression of miR-23a-3p promoted apoptosis and affected the cell cycle. NEAT1 repressed the expression of miR-23a-3p, and therefore promoted SMC1A, which in turn suppressed myeloid leukemia cell proliferation and enhanced apoptosis. K E Y W O R D S acute myeloid leukemia, long noncoding RNA, miR-23a-3p, NEAT1, SMC1A

Nonsense-mediated mRNA decay (NMD) is an evolutionarily conserved RNA decay mechanism that has emerged as a potent cell-intrinsic restriction mechanism of retroviruses and positive-strand RNA viruses. However, whether NMD is capable of restricting DNA viruses is not known. The DNA virus Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma and primary effusion lymphoma (PEL). Here, we demonstrate that NMD restricts KSHV lytic reactivation. Leveraging high-throughput transcriptomics we identify NMD targets transcriptome-wide in PEL cells and identify host and viral RNAs as substrates. Moreover, we identified an NMD-regulated link between activation of the unfolded protein response and transcriptional activation of the main KSHV transcription factor RTA, itself an NMD target. Collectively, our study describes an intricate relationship between cellular targets of an RNA quality control pathway and KSHV lytic gene expression, and demonstrates that NMD can function as a cell intrinsic restriction mechanism acting upon DNA viruses.

Voriconazole is a broad-spectrum antifungal agent for the treatment of invasive fungal infections. There is limited information about the pharmacokinetics and appropriate dosage of voriconazole in patients with liver dysfunction. This study aimed to explore the relationship between voriconazole trough concentration (C trough) and toxicity, identify the factors significantly associated with voriconazole pharmacokinetic parameters and propose an optimised voriconazole dosing regimen for patients with liver dysfunction. Methods: The study prospectively enrolled 51 patients with 272 voriconazole concentrations. Receiver operating characteristic curves were used to explore the relationship between voriconazole C trough and toxicity. The pharmacokinetic data was