Antiretroviral therapy inhibits HIV-1 replication but is not curative due to establishment of a persistent reservoir after virus integration into the host genome. Reservoir reduction is therefore an important HIV-1 cure strategy. Some HIV-1 nonnucleoside reverse transcriptase inhibitors induce HIV-1 selective cytotoxicity in vitro but require concentrations far exceeding approved dosages.
View Article and Find Full Text PDFCo-opting host cell protein synthesis is a hallmark of many virus infections. In response, certain host defense proteins limit mRNA translation globally, albeit at the cost of the host cell's own protein synthesis. Here, we describe an interferon-stimulated helicase, DDX60, that decreases translation from viral internal ribosome entry sites (IRESs).
View Article and Find Full Text PDFArgonaute (AGO) proteins bind small RNAs to silence complementary RNA transcripts, and they are central to RNA interference (RNAi). RNAi is critical for regulation of gene expression and antiviral defense in Aedes aegypti mosquitoes, which transmit Zika, chikungunya, dengue, and yellow fever viruses. In mosquitoes, AGO1 mediates miRNA interactions, while AGO2 mediates siRNA interactions.
View Article and Find Full Text PDFMature microRNAs (miRNAs) are a class of small noncoding RNA molecules involved in regulation of post-translational gene expression. Although aberrant levels of miRNAs have been found in various tumor tissues, their importance in tumor development and the molecular basis of their regulatory role remain unclear. Our bioinformatic analysis on The Cancer Genome Atlas database and microarray-based comparison of miRNA in different cell lines revealed that the level of mir-1287 is suppressed in hepatocellular carcinoma (HCC) cells.
View Article and Find Full Text PDFNon-structural protein 3 (NS3) is an essential enzyme and a therapeutic target of hepatitis C virus (HCV). Compared to NS3-catalyzed nucleic acids unwinding, its translation on single stranded nucleic acids have received relatively little attention. To investigate the NS3h translocation with single-stranded nucleic acids substrates directly, we have applied a hybrid platform of single-molecule fluorescence detection combined with optical trapping.
View Article and Find Full Text PDFHepatocellular carcinoma (HCC) causes significant medical burdens worldwide. Diagnosis, especially in the early stages, is still challenging. Therapeutic options are limited and often ineffective.
View Article and Find Full Text PDFGenomic DNA replication requires helicases to processively unwind duplexes. Although helicases encoded by positive-strand RNA viruses are necessary for RNA genome replication, their functions are not well understood. We determined structures of the hepatitis C virus helicase (NS3h) in complex with the transition state ATP mimic ADP·AlF4 (-) and compared them with the previous nucleic acid-associated ternary complexes.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
February 2015
Nonprimate hepacivirus (NPHV) is the closest known relative of hepatitis C virus (HCV) and its study could enrich our understanding of HCV evolution, immunity, and pathogenesis. High seropositivity is found in horses worldwide with ∼ 3% viremic. NPHV natural history and molecular virology remain largely unexplored, however.
View Article and Find Full Text PDFUnlabelled: Hepatitis C virus (HCV) is a widespread human pathogen causing liver cirrhosis and cancer. Similar to the case for other viruses, HCV depends on host and viral factors to complete its life cycle. We used proteomic and yeast two-hybrid approaches to elucidate host factors involved in HCV nonstructural protein NS5A function and found that MOBKL1B interacts with NS5A.
View Article and Find Full Text PDFApproximately 3% of the world population is infected with hepatitis C virus (HCV), causing a serious public health burden. Like other positive-strand RNA viruses, HCV assembles replicase complexes in association with cellular membranes and produces progeny RNA genomes through negative-strand intermediates. The viral proteins required for RNA replication are nonstructural (NS) proteins NS3 to NS5B.
View Article and Find Full Text PDFLysostaphin is a peptidoglycan hydrolase secreted by Staphylococcus simulans. It can specifically lyse Staphylococcus aureus and is being tested as a novel antibacterial agent. The protein contains an N-terminal catalytic domain and a C-terminal cell wall targeting domain.
View Article and Find Full Text PDFRNA capping enzyme (CE) is recruited specifically to RNA polymerase II (Pol II) transcription sites to facilitate cotranscriptional 5'-capping of pre-mRNA and other Pol II transcripts. The current model to explain this specific recruitment of CE to Pol II as opposed to Pol I and Pol III rests on the interaction between CE and the phosphorylated C-terminal domain (CTD) of Pol II largest subunit Rpb1 and more specifically between the CE nucleotidyltransferase domain and the phosphorylated CTD. Through biochemical and diffraction analyses, we demonstrate the existence of a distinctive stoichiometric complex between CE and the phosphorylated Pol II (Pol IIO).
View Article and Find Full Text PDFThe 5' guanine-N7 cap is the first cotranscriptional modification of messenger RNA. In Saccharomyces cerevisiae, the first two steps in capping are catalyzed by the RNA triphosphatase Cet1 and RNA guanylyltransferase Ceg1, which form a complex that is directly recruited to phosphorylated RNA polymerase II (RNAP IIo), primarily via contacts between RNAP IIo and Ceg1. A 3.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2010
A virally encoded superfamily-2 (SF2) helicase (NS3h) is essential for the replication of hepatitis C virus, a leading cause of liver disease worldwide. Efforts to elucidate the function of NS3h and to develop inhibitors against it, however, have been hampered by limited understanding of its molecular mechanism. Here we show x-ray crystal structures for a set of NS3h complexes, including ground-state and transition-state ternary complexes captured with ATP mimics (ADP.
View Article and Find Full Text PDFCurr Opin Struct Biol
February 2005
The 5' m7GpppN cap plays an essential role in the life cycle of eukaryotic mRNA and is required for efficient pre-mRNA splicing, export, stability and translation. Nascent pre-mRNA is capped through a series of three enzymatic steps that result in a 5' N7-methyl guanosine linked by an inverted 5'-5' triphosphate bridge to the first nucleotide of the transcript. Early structural studies revealed the mechanisms employed in the first two steps of capping, and more recent structural studies have completed the suite of capping activities and shed light on the mechanisms that target the capping apparatus to the phosphorylated C-terminal domain of RNA polymerase II.
View Article and Find Full Text PDFEukaryotic cells primarily utilize exoribonucleases and decapping enzymes to degrade their mRNA. Two major decapping enzymes have been identified. The hDcp2 protein catalyzes hydrolysis of the 5' cap linked to an RNA moiety, whereas the scavenger decapping enzyme, DcpS, functions on a cap structure lacking the RNA moiety.
View Article and Find Full Text PDFComplete removal of residual N-7 guanine cap from degraded messenger RNA is necessary to prevent accumulation of intermediates that might interfere with RNA processing, export, and translation. The human scavenger decapping enzyme, DcpS, catalyzes residual cap hydrolysis following mRNA degradation, releasing N-7 methyl guanosine monophosphate and 5'-diphosphate terminated cap or mRNA products. DcpS structures bound to m(7)GpppG or m(7)GpppA reveal an asymmetric DcpS dimer that simultaneously creates an open nonproductive DcpS-cap complex and a closed productive DcpS-cap complex that alternate via 30 A domain movements.
View Article and Find Full Text PDF