Inhibition of the erbB-2 tyrosine kinase receptor in breast cancer cells by phosphoromonothioate and phosphorodithioate antisense oligonucleotides.

Antisense activity against erbB-2 of a variety of sulfur-modified oligonucleotides was examined in a breast cancer cell line which overexpresses this oncogene. Using a 15 base anti-erbB-2 sequence previously shown to be effective, various backbone configurations containing phosphoromonothioate or phosphorodithioate linkages were evaluated for antisense activity by a two-color flow cytometric assay. This sequence was effective in inhibiting the production of erbB-2 protein when it was configured as a monothioate at each linkage and as an alternating dithioate/phosphodiester. Both of these compounds were also able to specifically inhibit erbB-2 mRNA expression, indicative of RNase H-mediated activity. The same sequence protected by either three dithioate or three monothioate linkages at each end was ineffective as an antisense reagent, suggesting that endonuclease activity is a significant determinant of the stability of oligonucleotides. Finally, the erbB-2 sequence target was shifted in an effort to improve antisense activity. A new lead sequence was identified that was significantly more effective in inhibiting erbB-2 protein levels and retained activity at lower concentrations.     

Surface distribution and internalization of erbB-2 proteins.

We report the localization over the cell surface and the early steps of antibody-induced internalization of the product of the erbB-2 proto-oncogene, structurally related to the epidermal growth factor receptor (EGFR). We show that erbB-2/p 185 is mostly excluded from endocytic pits on the cell surface. Incubation at 37 degrees C with an anti-erbB-2/p185 monoclonal antibody induces the rapid entry of the protein into the cell. Similar internalization is shown by a chimeric molecule EGFR/erbB-2 in response to EGF. Both the timing and the pathway of internalization followed by the erbB-2/p185 appear totally similar to those described for the EGFR. At variance with the normal erbB-2/p185, two mutant activated erbB-2 proteins are frequently localized within endocytic pits of the cell surface, indicating that mutations in the transmembrane regions may determine constitutive internalization of the protein.     

绿色荧光蛋白基因mRNA反义寡核苷酸的筛选和应用

基因mRNA的靶点筛选是设计反义寡核苷酸的关键.建立了PARASS(polyAanchoredRNAaccessiblesitesscreening)方法,即通过在mRNA末端引入polyA,与生物素标记的polyT退火结合,将其同链亲和素磁珠混合,使mRNA通过3’末端得到固定,保持mRNA的自然伸展和折叠,与寡核苷酸文库杂交筛选mRNA的结合靶点.PARASS筛选获得了绿色荧光蛋白(GFP)mRNA的3个反义寡核苷酸结合靶点,据其设计了多条反义寡核苷酸,与对照组相比,体外RNaseH分析显示3个靶点均为有效,在HeLa细胞内针对靶点的反义寡核苷酸能抑制GFP的表达,得到了Northern印迹结果支持.PARASS对反义寡核苷酸药物设计具有应用价值.     

Neurons are protected from excitotoxic death by p53 antisense oligonucleotides delivered in anionic liposomes.

The potential of anionic liposomes for oligonucleotide delivery was explored because the requirement for a net-positive charge on transfection-competent cationic liposome-DNA complexes is ambiguous. Liposomes composed of phosphatidylglycerol and phosphatidylcholine were monodisperse and encapsulated oligonucleotides with 40-60% efficiency. Ionic strength, bilayer charge density, and oligonucleotide chemistry influenced encapsulation. To demonstrate the biological efficacy of this vector, antisense oligonucleotides to p53 delivered in anionic liposomes were tested in an in vitro model of excitotoxicity. Exposure of hippocampal neurons to glutamate increased p53 protein expression 4-fold and decreased neuronal survival to approximately 35%. Treatment with 1 microm p53 antisense oligonucleotides in anionic liposomes prevented glutamate-induced up-regulation of p53 and increased neuronal survival to approximately 75%. Encapsulated phosphorothioate p53 antisense oligonucleotides were neuroprotective at 5-10-fold lower concentrations than when unencapsulated. Replacing the anionic lipid with phosphatidylserine significantly decreased neuroprotection. p53 antisense oligonucleotides complexed with cationic liposomes were ineffective. Neuroprotection by p53 antisense oligonucleotides in anionic liposomes was comparable with that by glutamate receptor antagonists and a chemical inhibitor of p53. Anionic liposomes were also capable of delivering plasmids and inducing transgene expression in neurons. Anionic liposome-mediated internalization of Cy3-labeled oligonucleotides by neurons and several other cell lines demonstrated the universal applicability of this vector.     

MDM2反义寡核苷酸联合紫杉醇对乳腺癌MCF-7细胞株的作用

目的:探讨靶向MDM2反义寡核苷酸(ASON)联合紫杉醇对乳腺癌MCF-7细胞株的影响。方法:合成一段与MDM2 mRNA特异性结合的反义寡核苷酸和与反义寡核苷酸有4个碱基不同的的错义寡核苷酸(MON),脂质体2000介导不同浓度的MDM2ASON转染MCF-7乳腺癌细胞系,转染的乳腺癌细胞通过1μmol/L紫杉醇药物处理后,采用RT-PCR和Western Blot方法检测MDM2 ASON联合紫杉醇的协同作用及对乳腺癌MCF-7细胞株的抑制效率,MTT观察给药后MCF-7细胞的增殖能力和药物敏感性。结果:MDM2反义寡核苷酸联合紫杉醇明显下调MDM2 mRNA及MDM2蛋白表达水平,抑制MCF-7细胞的生长,随着MDM2 ASON浓度的增加,MDM2表达越来越低,协同作用越来越强,呈剂量依赖关系,A500联合紫杉醇的协同作用最明显,MTT显示紫杉醇处理的转染MCF-7细胞增殖抑制率明显增高,A500抑制增殖作用最明显,抑制率达(13.0±0.84)%。结论:不同浓度MDM2 ASON转染后的乳腺癌MCF-7细胞,等浓度紫杉醇处理后,乳腺癌MCF-7细胞MDM2表达明显降低,细胞凋亡增加,,MDM2 ASON联合紫杉醇对MCF-7细胞有协同作用,提高了乳腺癌MCF-7细胞对紫杉醇的药物敏感性。     

Inhibition of the androgen receptor by antisense oligonucleotides regulates the biological activity of androgens in SZ95 sebocytes.

One novel strategy for the blockade of the androgen receptor could be the selective inhibition of androgen receptor by antisense oligonucleotides or small interfering RNA molecules. Here we describe the down regulation of the androgen receptor in cultured human SZ95 sebocytes with antisense oligonucleotides modified with phosphorothioates and 2'- O-methylribosyl residues. The ability of antisense oligonucleotides to cross the cellular membrane was enhanced by establishing a transient transfection system based on cationic lipid vesicles. Both antisense oligonucleotide types administered caused assumedly translational arrest. Dose-dependent inhibition of androgen receptor protein expression was observed after SZ95 sebocyte transfection with modified phosphorothioate oligonucleotides and modified 2'- O-methylribonucleotides which were directed against the translational start of the androgen receptor mRNA. The strongest transient inhibition of androgen receptor expression was detected after 14 hours with 1.0 muM antisense 2'- O-methylribonucleotides (88+/-1.3%, p<0.001). With longer recovery times than 24 hours, androgen receptor protein expression returned to the native control levels. Inhibition of the expression of androgen receptor by antisense oligonucleotides, reduced the enhanced proliferation of SZ95 sebocytes challenged by testosterone and 5alpha-dihydrotestosterone. This administration opens new therapeutic possibilities in androgen-associated skin diseases, since we could also show androgen inhibition with these antisense oligonucleotides in a reconstituted human epidermis model (Horm Metab Res 2007; 39:157-165).     

The human ubiquitin-conjugating enzyme Cdc34 controls cellular proliferation through regulation of p27Kip1 protein levels

Ubiquitin-mediated degradation of the cyclin-dependent kinase inhibitor p27Kip1 was shown to be required for the activation of key cyclin-dependent kinases, thereby triggering the onset of DNA replication and cell cycle progression. Although the SCFSkp2 ubiquitin ligase has been reported to mediate p27Kip1 degradation, the nature of the human ubiquitin-conjugating enzyme involved in this process has not yet been determined at the cellular level. Here, we show that antisense oligonucleotides targeting the human ubiquitin-conjugating enzyme Cdc34 downregulate its expression, inhibit the degradation of p27Kip1, and prevent cellular proliferation. Elevation of p27Kip1 protein level is found to be the sole requirement for the inhibition of cellular proliferation induced upon downregulation of Cdc34. Indeed, reducing the expression of p27Kip1 with a specific antisense oligonucleotide is sufficient to reverse the anti-proliferative phenotype elicited by the Cdc34 antisense. Furthermore, downregulation of Cdc34 is found to specifically increase the abundance of the SCFSkp2) ubiquitin ligase substrate p27Kip1, but has no concomitant effect on the level of IkBalpha and beta-catenin, which are known substrates of a closely related SCF ligase.     

靶向Survivin的反义寡核苷酸对肿瘤细胞增殖的抑制作用

 Survivin是新近克隆的一种凋亡抑制蛋白 (IAP)家族成员 ,在几乎所有肿瘤组织中特异性表达 ,而在正常成年终末分化组织中低表达甚至不表达 .采用四唑盐 (MTT)比色实验法比较 2 0条抗人survivin反义寡核苷酸对HeLa细胞增殖的抑制效果 ,并从中筛选效果显著的反义寡核苷酸 ,在体外水平进一步验证其抑制survivin表达的能力 .在用 4 0 0nmol L反义寡核苷酸转染HeLa细胞 4 8h后 ,有 4条反义寡核苷酸对细胞增殖的抑制率超过 4 0 %,其中 4 5号反义寡核苷酸的抑制率可达5 9%,而阳性对照序列ISIS2 372 2的抑制率仅达 30 %.Northern和Western印迹分析证明 :4 5号反义寡核苷酸可明显降低细胞中survivin基因的mRNA含量和蛋白水平 .4 5号反义寡核苷酸还可在较低浓度 (2 0 0nmol L)显著增强HeLa细胞对化疗药三尖杉酯碱的敏感性 .因此 ,4 5号反义寡核苷酸有望应用于survivin高表达肿瘤的辅助治疗之中     

Antisense oligonucleotide inhibition of hepatitis C virus gene expression in transformed hepatocytes.

Genetic and biochemical studies have provided convincing evidence that the 5' noncoding region (5' NCR) of hepatitis C virus (HCV) is highly conserved among viral isolates worldwide and that translation of HCV is directed by an internal ribosome entry site (IRES) located within the 5' NCR. We have investigated inhibition of HCV gene expression using antisense oligonucleotides complementary to the 5' NCR, translation initiation codon, and core protein coding sequences. Oligonucleotides were evaluated for activity after treatment of a human hepatocyte cell line expressing the HCV 5' NCR, core protein coding sequences, and the majority of the envelope gene (E1). More than 50 oligonucleotides were evaluated for inhibition of HCV RNA and protein expression. Two oligonucleotides, ISIS 6095, targeted to a stem-loop structure within the 5' NCR known to be important for IRES function, and ISIS 6547, targeted to sequences spanning the AUG used for initiation of HCV polyprotein translation, were found to be the most effective at inhibiting HCV gene expression. ISIS 6095 and 6547 caused concentration-dependent reductions in HCV RNA and protein levels, with 50% inhibitory concentrations of 0.1 to 0.2 microM. Reduction of RNA levels, and subsequently protein levels, by these phosphorothioate oligonucleotides was consistent with RNase H cleavage of RNA at the site of oligonucleotide hybridization. Chemically modified HCV antisense phosphodiester oligonucleotides were designed and evaluated for inhibition of core protein expression to identify oligonucleotides and HCV target sequences that do not require RNase H activity to inhibit expression. A uniformly modified 2'-methoxyethoxy phosphodiester antisense oligonucleotide complementary to the initiator AUG reduced HCV core protein levels as effectively as phosphorothioate oligonucleotide ISIS 6095 but without reducing HCV RNA levels. Results of our studies show that HCV gene expression is reduced by antisense oligonucleotides and demonstrate that it is feasible to design antisense oligonucleotide inhibitors of translation that do not require RNase H activation. The data demonstrate that chemically modified antisense oligonucleotides can be used as tools to identify important regulatory sequences and/or structures important for efficient translation of HCV.     

bFGF反义寡核苷酸增强鼠黑色素瘤B16细胞化疗药物敏感性研究

目的:研究bFGF反义硫代寡核苷酸增强肿瘤细胞对化疗药物敏感性作用。方法:设计、合成bFGF寡核苷酸,用聚乙烯亚胺(polyemyleneimine,PEI)介导bFGF反义硫代寡核苷酸转染入黑色素瘤B16细胞,MTT法检测bFGF反义硫代寡核苷酸及其与化疗药物联合处理后的细胞增殖率;半定量RT-PCR测定bFGF反义硫代寡核苷酸转染后细胞中bFGF mRNA水平;流式细胞仪分析bFGF反义硫代寡核苷酸诱导的细胞凋亡。结果:bFGF反义硫代寡核苷酸对B16细胞增殖的抑制率为64.8%,且呈剂量依赖效应。B16细胞中bFGF mRNA被bFGF反义硫代寡核苷酸显著降低,为对照细胞的57.9%,且bFGF反义硫代寡核苷酸诱导B16细胞凋亡,凋亡率为41.8%。bFGF反义硫代寡核苷酸转染能显著增强B16细胞对阿霉素、5-氟脲嘧啶及顺铂的敏感性,非特异性硫代寡核苷酸不影响阿霉素、5-氟脲嘧啶及顺铂抑制B16细胞增殖。结论:bFGF反义硫代寡核苷酸显著增强B16细胞的化疗敏感性,表明其可协同化疗药物用于治疗肿瘤。     

Antinociceptive effect of antisense oligonucleotides against the vanilloid receptor VR1/TRPV1

To examine the role of the vanilloid receptor TRPV1 in neuropathic pain, we assessed the effects of the receptor antagonist thioxo-BCTC and antisense oligonucleotides against the TRPV1 mRNA in a rat model of spinal nerve ligation. In order to identify accessible sites on the mRNA of TRPV1, the RNase H assay was used, leading to the successful identification of binding sites for antisense oligonucleotides. Cotransfection studies using Cos-7 cells were employed to identify the most effective antisense oligonucleotide efficiently inhibiting the expression of a fusion protein consisting of TRPV1 and the green fluorescent protein in a specific and concentration-dependent manner. In an in vivo rat model of spinal nerve ligation, intravenous application of the TRPV1 antagonist thioxo-BCTC reduced mechanical hypersensitivity yielding an ED(50) value of 10.6mg/kg. Intrathecal administration of the antisense oligonucleotide against TRPV1, but not the mismatch oligonucleotide or a vehicle control, reduced mechanical hypersensitivity in rats with spinal nerve ligation in a similar manner. Immunohistochemical analysis revealed neuropathy- and antisense-associated regulation of TRPV1 protein expression in spinal cord and dorsal root ganglia. Our data demonstrate comparative analgesic effects of a TRPV1 anatagonist and a rationally designed TRPV1 antisense oligonucleotide in a spinal nerve ligation model of neuropathic pain and thus, lend support to the validation of TRPV1 as a promising target for the treatment of neuropathic pain.     

Concerted effect of transforming growth factor-beta, cyclin inhibitor p21, and c-myc on smooth muscle cell proliferation

Increased aortic smooth muscle cell (SMC) proliferation is a key event in the pathogenesis of atherosclerosis. Transforming growth factor-beta (TGF-beta) is one of the potent inhibitors of SMC proliferation. The purpose of this study was 1) to explore the effect of TGF-beta inhibition on proliferation of SMC and expression of growth regulatory molecules like p21 and c-myc and 2) to determine whether restoration of cell cycle regulatory molecules normalizes the altered proliferation. To test the role of TGF-beta in SMC proliferation, using antisense plasmid DNA, we inhibited TGF-beta gene from aortic SMC, which resulted in a significant increase (P < 0.03) in proliferation (studied by quantifying new DNA synthesis with [(3)H]thymidine uptake assay). In TGF-beta-altered SMC (TASMC), the mRNA expression (studied by RT-PCR) of c-myc was increased whereas that of the cyclin inhibitor p21 was completely inhibited. Using p21 sense plasmid DNA, we transfected p21 gene in TASMC, which restored p21 mRNA and protein expression and decreased proliferation (P < 0.002) in TASMC. Similar treatment with c-myc antisense oligonucleotides significantly (P < 0.001) decreased the proliferation of TASMC. TASMC also exhibited alteration in morphological changes in SMC but returned to normal with treatment of p21 and TGF-beta sense plasmid DNA. Two-dimensional gel electrophoresis analysis of SMC and TASMC demonstrated differential expression of proteins relevant to cellular proliferation and atherosclerosis. This study uniquely analyzes the effect of TGF-beta at the molecular level on proliferation of SMC and on cell cycle regulatory molecules, implicating their potential role in the pathogenesis of atherosclerosis.     

Heregulin-beta is especially potent in activating phosphatidylinositol 3-kinase in nontransformed human mammary epithelial cells

The neu differentiation factors/heregulins (HRGs) comprise a family of polypeptide growth factors that activate p185(erbB-2) through direct binding to either erbB-3 or erbB-4 receptor tyrosine kinases. We have previously shown that HRG-beta is mitogenic for various human mammary epithelial cell lines that coexpress c-erbB-2 and c-erbB-3. Phosphatidylinositol 3-kinase (PI3K) is activated by p185(erbB-2) /erbB-3 heterodimers in cells stimulated by HRG, and PI3K is constitutively activated by p185(erbB-2) /erbB-3 in breast carcinoma cells that overexpress c-erbB-2. To better understand the relative abilities of HRGs, epidermal growth factor (EGF), or insulin to activate PI3K under normal physiological conditions, we compared the levels of recruitment of the 85-kDa regulatory subunit of PI3K when activated by the type I (erbB) or type II [insulin-like growth factor (IGF)] receptor tyrosine kinases in two different nontransformed human mammary epithelial cell lines. The nontransformed H16N-2 cells isolated from normal tissue express EGFR, p185(erbB-2), and erbB-3, and are highly responsive to the mitogenic effects of HRG-beta as well as to the combination of EGF and insulin in serum-free culture. We measured the stoichiometry of p85 recruited by tyrosine-phosphorylated proteins induced in H16N-2 cells by either the alpha or the beta isoform of HRG. HRG-beta was greater than 10-fold more potent in inducing p85 recruitment than was the less biologically active HRG-alpha isoform. HRG-beta was also a more potent inducer of p85 recruited by tyrosine-phosphorylated proteins than was either EGF, insulin, or EGF and insulin combined. Furthermore, erbB-3 principally mediated the direct recruitment of p85 in cells stimulated by HRG or EGF, indicating that, in addition to the high-level activation of PI3K by p185(erbB-2) / erbB-3, EGFR/erbB-3 heterodimer interaction is essential for the weak but significant level of PI3K activated by EGF in cells that express normal EGFR levels. Studies using the PI3K inhibitor wortmannin also indicated that PI3K activation was required for the proliferation of H16N-2 cells induced by either HRG-beta or EGF and insulin in serum-free culture. Finally, HRG-beta was also an especially potent inducer of PI3K in the nontransformed MCF-10A cells, which were derived spontaneously from normal reduction mammoplasty tissue. These data show, for the first time, a side-by-side quantitative comparison of the relative degree of PI3K activated by different growth factors in nontransformed growth factor-dependent cells under precisely defined conditions in culture.     

Properties of the cysteine-less Pho84 phosphate transporter of Saccharomyces cerevisiae

The murine 3T3-L1 preadipocyte cell line is well characterized for its capacity to undergo differentiation into adipocytes under appropriate hormonal stimulation. p107, a member of the retinoblastoma tumor suppressor gene family has been shown to be dramatically upregulated during the early requisite clonal expansion phase of 3T3-L1 adipogenesis; however, a functional consequence has yet to be described. A phosphorothioate antisense RNA approach was utilized to determine if inhibition of p107 expression would block or perturb adipocyte differentiation. A series of three phosphorothioate oligonucleotides in antisense orientation was generated, designated AS1, AS2, and AS3 along with a sense control oligonucleotide complementary to AS1 and added to postconfluent cells at a concentration of 20 and 50 microM throughout hormonally stimulated differentiation. Treatment of cells with either concentration of the sense, AS1, AS2, or 20 microM AS3 oligonucleotides had little effect on either Oil Red O lipid accumulation or induction of p107 protein levels. In contrast, treatment with 50 microM AS3 inhibited the increase in p107 protein levels and led to a complete block in differentiation as detected by Oil Red O lipid accumulation and inhibition of adipocyte-specific mRNA expression. In addition, treatment with AS3 led to a significant inhibition of cellular proliferation associated with clonal expansion. Combined, these results provide strong evidence supporting a functional role for p107 in 3T3-L1 adipocyte differentiation.     

Expression of ssDNA in mammalian cells

Antisense therapy involves the use of antisense oligonucleotides for altering targeted gene function. However, the low efficiency of cell delivery of antisense oligonucleotides has limited the efficacy of antisense therapeutic approaches. RNA-based antisense or ribozyme oligonucleotides can be either synthesized endogenously (e.g., by a viral vector) or delivered exogenously. However, there is presently no vector delivery system available for DNA-based oligonucleotides. Recently, a novel ssDNA expression vector that can generate intracellularly any ssDNA molecule, such as antisense oligonucleotide or DNA enzyme, has been developed in our laboratory. Here we describe an improved expression vector based on the first-generation two-vector system. To test this new expression vector, we chose to express a single-stranded "10-23" DNA enzyme targeting c-raf mRNA in the human lung carcinoma A549 cell line. After introduction into cells by transient transfection, c-raf-cleaving DNA enzymes produced by this expression vector can significantly suppress the expression of c-raf mRNA. Furthermore, the expressed c-raf DNA enzymes induced cell apoptosis, as indicated by genomic DNA fragmentation assay. Our study further demonstrates the feasibility of using this novel ssDNA expression technology to produce intracellularly any sequence of interest, including antisense oligonucleotides and DNA enzyme molecules.     

Antisense Oligodeoxynucleotide Complementary to CXCR4 mRNA Block Replication of HIV-1 in COS Cells

Abstract

CXCR4 is both a chemokine receptor and an entry co-receptor for the T-cell line-adapted human immunodeficiency virus type 1 (HIV-1). To find a more efficacious therapeutic treatement of acquied immunodeficiency syndrome, we exmined the effects of antisense oligonucleotides on CXCR4 production. COS cells, stably expressing CXCR4 and CD4, were incubated with several kinds of oligonucleotides. Total human p24 antigen production was determined using an enzyme-linked immunosorbent assay system. An antisense phosphorothioate-modified oligonucleotide, complementary to the translation region of the CXCR4 mRNA, showed minimal inhibition of p24 antigen production at the high concentration of 2μM. On the other hand, the antisense phosphorothioate oligonucleotide, when used with transfection reagents, showed high efficiency at low concentrations, and confirmed the sequence-specific action. Interestingly, the oligonucleotide with the natual phosphodiester backbone, when used with the transfection reagents, also had high functional effects, comparable to the modified oligonucleotide. This defines the prerequisite criteria necessary for the design and the application of antisense oligonucleotides against HIV-1 in vivo.     

Antisense Knockdown of Glutamate Transporters Alters the Subfield Selectivity of Kainate-Induced Cell Death in Rat Hippocampal Slice Cultures

Organotypic rat hippocampal slice cultures were used to study the role of excitatory amino acid transporters (EAATs) in kainate-induced cell death. Expression of the neuronal (EAAT3) or glial (EAAT2) transporters was inhibited with antisense phosphothioate oligonucleotides, and cytotoxicity was assessed with propidium iodide uptake. In control cultures, a concentration of 10 microM kainate was more cytotoxic in CA3 than in CA1. Treatment for 24 h with EAAT3 antisense oligonucleotide decreased kainate toxicity in CA1 but had an opposite effect in CA3. Neither antisense oligonucleotide to EAAT2 nor mismatch oligonucleotide to EAAT3 decreased kainate toxicity in CA1. Immunoblotting with affinity-purified antibodies showed that EAAT3 antisense oligonucleotide decreased selectively EAAT3 but not EAAT2 protein levels, and vice versa. NMDA was more cytotoxic in CA1 than in CA3, and antisense oligonucleotides to either EAAT3 or EAAT2 did not decrease the NMDA effect in CA1 or CA3. Dihydrokainate and DL-threo-beta-hydroxyaspartic acid were more cytotoxic in CA1 than in CA3, suggesting that the higher vulnerability of CA3 to kainate was not the result of its activity as transporter blocker. We conclude that glutamate transporters differentially regulate excitotoxicity in different hippocampal subfields.     

Inhibition of translation of hepatitis C virus RNA by 2-modified antisense oligonucleotides.

Inhibition of hepatitis C virus (HCV) gene expression by antisense oligonucleotides was investigated using both a rabbit reticulocyte lysate in vitro translation assay and a transformed human hepatocyte cell expression assay. Screening of overlapping oligonucleotides complementary to the HCV 5' noncoding region and the core open reading frame (ORF) identified a region susceptible to translation inhibition between nucleotides 335 and 379. Comparison of 2'-deoxy-, 2'-O-methyl-, 2'-O-methoxyethyl-, 2'-O-propyl-, and 2'-fluoro-modified phosphodiester oligoribonucleotides demonstrated that increased translation inhibition correlated with both increased binding affinity and nuclease stability. In cell culture assays, 2'-O-methoxyethyl-modified oligonucleotides inhibited HCV core protein synthesis with comparable potency to phosphorothioate oligodeoxynucleotides. Inhibition of HCV core protein expression by 2'-modified oligonucleotides occurred by an RNase H-independent translational arrest mechanism.