Synthesis and Screening of a DNA-Encoded Library of Non-Peptidic Macrocycles.

There is considerable interest in the development of libraries of non-peptidic macrocycles as a source of ligands for difficult targets. We report here the solid-phase synthesis of a DNA-encoded library of several hundred thousand thioether-linked macrocycles. The library was designed to be highly diverse with respect to backbone scaffold diversity and to minimize the number of amide N-H bonds, which compromise cell permeability. The utility of the library as a source of protein ligands is demonstrated through the isolation of compounds that bind Streptavidin, a model target, with high affinity.

Endonasal CNS Delivery System for Blood-Brain Barrier Impermeant Therapeutic Oligonucleotides Using Heterotopic Mucosal Engrafting.

The most significant obstacle in the treatment of neurological disorders is the blood-brain barrier (BBB), which prevents 98% of all potential neuropharmaceuticals from reaching the central nervous system (CNS). Brain derived neurotrophic factor (BDNF) is one of the most intensely studied targets in Parkinson's disease (PD) as it can reverse disease progression. BDNF AntagoNAT's (ATs) are synthetic oligonucleotide-like compounds capable of upregulating endogenous BDNF expression. Despite the significant promise of BDNF AT therapies for PD, they cannot cross the blood-brain barrier (BBB). Our group has developed an innovative endonasal heterotopic mucosal grafting technique to provide a permanent method of permeabilizing the BBB. This method is based on established endoscopic surgical procedures currently used in routine clinical practice. Our overall goal for the study was to investigate the distribution and efficacy of BDNF AT's using an extra-cranial graft model in naïve rats using the innovative heterotopic mucosal engrafting technique. BDNF AT cationic liposomes (ideal size range 200-250 nm) were developed and characterized to enhance the delivery to rat brain. Uptake, distribution and transfection efficiency of BDNF AntagoNAT's in saline and liposomes were evaluated qualitatively (microscopy) and quantitatively (ELISA and AT hybridization assays) in RT4-D6P2T rat schwannoma cells and in naïve rats. In vivo therapeutic efficacy of BDNF AT's encapsulated in liposomes was evaluated in a 6-OHDA toxin model of PD using western blot and tyrosine hydroxylase immunohistochemistry. Using complimentary in vitro and in vivo techniques, our results demonstrate that grafts are capable of delivering therapeutic levels of BDNF ATs in liposomes and saline formulation throughout the brain resulting in significant BDNF upregulation in key end target regions relevant to PD. BDNF AT liposomes resulted in a better distribution in rat brain as compared to saline control. The delivered BDNF AT's encapsulated in liposomes also conferred a neuroprotective effect in a rat 6-OHDA model of PD. As a platform technique, these results further suggest that this approach may be utilized to deliver other BBB impermeant oligonucleotide-based therapeutics thereby opening the door to additional treatment options for CNS disease.

Regulation of the apolipoprotein gene cluster by a long noncoding RNA.

Apolipoprotein A1 (APOA1) is the major protein component of high-density lipoprotein (HDL) in plasma. We have identified an endogenously expressed long noncoding natural antisense transcript, APOA1-AS, which acts as a negative transcriptional regulator of APOA1 both in vitro and in vivo. Inhibition of APOA1-AS in cultured cells resulted in the increased expression of APOA1 and two neighboring genes in the APO cluster. Chromatin immunoprecipitation (ChIP) analyses of a ∼50 kb chromatin region flanking the APOA1 gene demonstrated that APOA1-AS can modulate distinct histone methylation patterns that mark active and/or inactive gene expression through the recruitment of histone-modifying enzymes. Targeting APOA1-AS with short antisense oligonucleotides also enhanced APOA1 expression in both human and monkey liver cells and induced an increase in hepatic RNA and protein expression in African green monkeys. Furthermore, the results presented here highlight the significant local modulatory effects of long noncoding antisense RNAs and demonstrate the therapeutic potential of manipulating the expression of these transcripts both in vitro and in vivo.

High-throughput screening of the yeast kinome: identification of human serine/threonine protein kinases that phosphorylate the hepatitis C virus NS5A protein.

The hepatitis C virus NS5A protein plays a critical role in virus replication, conferring interferon resistance to the virus through perturbation of multiple intracellular signaling pathways. Since NS5A is a phosphoprotein, it is of considerable interest to understand the role of phosphorylation in NS5A function. In this report, we investigated the phosphorylation of NS5A by taking advantage of 119 glutathione S-transferase-tagged protein kinases purified from Saccharomyces cerevisiae to perform a global screening of yeast kinases capable of phosphorylating NS5A in vitro. A database BLAST search was subsequently performed by using the sequences of the yeast kinases that phosphorylated NS5A in order to identify human kinases with the highest sequence homologies. Subsequent in vitro kinase assays and phosphopeptide mapping studies confirmed that several of the homologous human protein kinases were capable of phosphorylating NS5A. In vivo phosphopeptide mapping revealed phosphopeptides common to those generated in vitro by AKT, p70S6K, MEK1, and MKK6, suggesting that these kinases may phosphorylate NS5A in mammalian cells. Significantly, rapamycin, an inhibitor commonly used to investigate the mTOR/p70S6K pathway, reduced the in vivo phosphorylation of specific NS5A phosphopeptides, strongly suggesting that p70S6 kinase and potentially related members of this group phosphorylate NS5A inside the cell. Curiously, certain of these kinases also play a major role in mRNA translation and antiapoptotic pathways, some of which are already known to be regulated by NS5A. The findings presented here demonstrate the use of high-throughput screening of the yeast kinome to facilitate the major task of identifying human NS5A protein kinases for further characterization of phosphorylation events in vivo. Our results suggest that this novel approach may be generally applicable to the screening of other protein biochemical activities by mechanistic class.

The regulation of hepatitis C virus (HCV) internal ribosome-entry site-mediated translation by HCV replicons and nonstructural proteins.

Hepatitis C virus (HCV), the global leading cause of chronic liver disease, has a positive-sense, ssRNA genome that encodes a large polyprotein. HCV polyprotein translation is initiated by an internal ribosome-entry site (IRES) located at the 5' end of the viral genome, in a cap-independent manner, but the regulatory mechanism of this process remains poorly understood. In this study, we characterized the effect of HCV nonstructural proteins on HCV IRES-directed translation in both HCV replicon cells and transiently transfected human liver cells expressing HCV nonstructural proteins. Using bicistronic reporter gene constructs carrying either HCV or other viral IRES sequences, we found that the HCV IRES-mediated translation was specifically upregulated in HCV replicon cells. This enhancement of HCV IRES-mediated translation by the replicon cells was inhibited by treatment with either type I interferon or ribavirin, drugs that perturb HCV genome replication, suggesting that the enhancement is probably due to HCV-encoded protein function(s). Reduced phosphorylation levels of both eIF2alpha and eIF4E were observed in the replicon cells, which is consistent with our previous findings and indicates that the NS5A nonstructural protein may be involved in the regulatory mechanism(s). Indeed, transient expression of NS5A or NS4B in human liver cells stimulated HCV IRES activity. Interestingly, mutation in the ISDR of NS5A perturbed this stimulation of HCV IRES activity. All these results suggest, for the first time, that HCV nonstructural proteins preferentially stimulate the viral cap-independent, IRES-mediated translation.

System-based proteomic analysis of the interferon response in human liver cells.

BACKGROUND: Interferons (IFNs) play a critical role in the host antiviral defense and are an essential component of current therapies against hepatitis C virus (HCV), a major cause of liver disease worldwide. To examine liver-specific responses to IFN and begin to elucidate the mechanisms of IFN inhibition of virus replication, we performed a global quantitative proteomic analysis in a human hepatoma cell line (Huh7) in the presence and absence of IFN treatment using the isotope-coded affinity tag (ICAT) method and tandem mass spectrometry (MS/MS). RESULTS: In three subcellular fractions from the Huh7 cells treated with IFN (400 IU/ml, 16 h) or mock-treated, we identified more than 1,364 proteins at a threshold that corresponds to less than 5% false-positive error rate. Among these, 54 were induced by IFN and 24 were repressed by more than two-fold, respectively. These IFN-regulated proteins represented multiple cellular functions including antiviral defense, immune response, cell metabolism, signal transduction, cell growth and cellular organization. To analyze this proteomics dataset, we utilized several systems-biology data-mining tools, including Gene Ontology via the GoMiner program and the Cytoscape bioinformatics platform. CONCLUSIONS: Integration of the quantitative proteomics with global protein interaction data using the Cytoscape platform led to the identification of several novel and liver-specific key regulatory components of the IFN response, which may be important in regulating the interplay between HCV, interferon and the host response to virus infection.