SEARCH · Search PubMed

Results for “Enhancer RNAs”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources

PubMed1985

Enhancer-facilitated expression of a human H4 histone gene.

Cultured mammalian cells were transfected with a recombinant human H4 histone gene. S1 nuclease mapping of cellular RNAs from transfected cells revealed: (i) correct initiation of transcription at the cap site, with some transcripts originating from other sites in the 5' flanking region of this H4 gene; (ii) cis-linkage of an SV-40 transcriptional enhancer element upstream of the H4 5'-flanking region resulted in about a 50-fold increase in the level of correctly initiated H4 mRNA and (iii) in a heterologous murine system stability of human H4 mRNAs was apparently sensitive to inhibition of DNA-synthesis by hydroxyurea. Our results suggest that certain sequences required for the initiation of a human H4 histone gene transcript reside within the 210 nucleotides immediately upstream from the cap site and that the level of expression is influenced by the introduction of an enhancer element.

Animals↗

PubMed2004

Synthetic dsRNA Dicer substrates enhance RNAi potency and efficacy.

RNA interference (RNAi) is the process of sequence-specific post-transcriptional gene silencing triggered by double-stranded RNAs. In attempts to identify RNAi triggers that effectively function at lower concentrations, we found that synthetic RNA duplexes 25-30 nucleotides in length can be up to 100-fold more potent than corresponding conventional 21-mer small interfering RNAs (siRNAs). Some sites that are refractory to silencing by 21-mer siRNAs can be effectively targeted by 27-mer duplexes, with silencing lasting up to 10 d. Notably, the 27-mers do not induce interferon or activate protein kinase R (PKR). The enhanced potency of the longer duplexes is attributed to the fact that they are substrates of the Dicer endonuclease, directly linking the production of siRNAs to incorporation in the RNA-induced silencing complex. These results provide an alternative strategy for eliciting RNAi-mediated target cleavage using low concentrations of synthetic RNA as substrates for cellular Dicer-mediated cleavage.

Gene Expression Regulation↗

PubMed2000

The human cytomegalovirus major immediate-early distal enhancer region is required for efficient viral replication and immediate-early gene expression.

The human cytomegalovirus (HCMV) major immediate-early (MIE) genes, encoding IE1 p72 and IE2 p86, are activated by a complex enhancer region (base positions -65 to -550) that operates in a cell type- and differentiation-dependent manner. The expression of MIE genes is required for HCMV replication. Previous studies analyzing functions of MIE promoter-enhancer segments suggest that the distal enhancer region variably modifies MIE promoter activity, depending on cell type, stimuli, or state of differentiation. To further understand the mechanism by which the MIE promoter is regulated, we constructed and analyzed several different recombinant HCMVs that lack the distal enhancer region (-300 to -582, -640, or -1108). In human fibroblasts, the HCMVs without the distal enhancer replicate normally at high multiplicity of infection (MOI) but replicate poorly at low MOI in comparison to wild-type virus (WT) or HCMVs that lack the neighboring upstream unique region and modulator (-582 or -640 to -1108). The growth aberrancy was normalized after restoring the distal enhancer in a virus lacking this region. For HCMVs without a distal enhancer, the impairment in replication at low MOI corresponds to a deficiency in production of MIE RNAs compared to WT or virus lacking the unique region and modulator. An underproduction of viral US3 RNA was also evident at low MOI. Whether lower production of IE1 p72 and IE2 p86 causes a reduction in expression of the immediate-early (IE) class US3 gene remains to be determined. We conclude that the MIE distal enhancer region possesses a mechanism for augmenting viral IE gene expression and genome replication at low MOI, but this regulatory function is unnecessary at high MOI.

Cells, Cultured↗

PubMed1989

Circular RNAs: relics of precellular evolution?

The demonstration of enzymatic capabilities of certain RNAs, in addition to their well-known template properties, has led to the recognition that RNAs are the only biological macromolecules that can function both as genotype and phenotype, hence raising the possibility of Darwinian selection and precellular evolution at the RNA level in the absence of DNA or protein. Recent models of such precellular RNA systems are patterned after the properties of intron-derived ribozymes. On the basis of a phylogenetic analysis and known properties of certain small plant pathogenic RNAs (viroids and viroid-like satellite RNAs), I suggest that these plant RNAs are more plausible candidates than introns as "living fossils" of a precellular RNA world. Their small size and circularity would have enhanced probability of their survival in error-prone, primitive self-replicating RNA systems and assured complete replication without the need for initiation or termination signals. All of these RNAs possess efficient mechanisms for the precise cleavage of monomers from oligomeric replication intermediates. Some (most viroids) require a host factor, but others (viroid-like satellite RNAs and one viroid) function as self-cleaving RNA enzymes far smaller and simpler than those derived from introns. The question is raised whether introns could have evolved from viroids or viroid-like satellite RNAs rather than vice versa, as has been widely speculated.

Base Sequence↗

PubMed1979

Hormonal control of gene expression: differential activation of rat bone marrow RNA polymerases by erythropoietin and testosterone.

Hormones play a role in the regulation of gene expression by inducing changes in enzyme patterns in target cells mediated by the synthesis of specific RNA molecules. Erythropoiesis has been used as a system for studying the molecular mechanism of regulation of gene action by means of two hormones: erythropoietin and testosterone. Experiments designed to correlate the biochemical action of both hormones on rat marrow cells are herein reported. Both factors seems to act at different biochemical and citological levels. Erythropoietin triggers the erythropoietic process acting on the erythropoietin sensitive cells (ESC), in which the hormone induces the synthesis of a high molecular weight RNA, which is the precursor of a functional 9 S messenger RNA. Testosterone seems to act on polychromatophilic erythroblasts, in which the synthesis of ribosomal RNA or its precursor is stimulated. The steroid enhances the nuclear ribonuclease activity, which could represent a control mechanism for the processing (maturation) of high molecular weight RNAs. The incorporation of 3H-GTP and 3H-UTP into RNA by isolated rat bone marrow nuclei is stimulated by erythropoietin and testosterone. Using alpha-amanitine and different ionic strength conditions it was found that erythropoietin enhances preferentially RNA polymerase II activity while testosterone increases RNA polymerase I activity. It is postulated that erythropoietin and testosterone act synergically to create the biochemical machinery for hemoglobin synthesis, the macromolecule that characterizes the erythropoietic process.

Amanitins↗

PubMed2003

Regulation of BRCC, a holoenzyme complex containing BRCA1 and BRCA2, by a signalosome-like subunit and its role in DNA repair.

We have isolated a holoenzyme complex termed BRCC containing BRCA1, BRCA2, and RAD51. BRCC not only displays increased association with p53 following DNA damage but also ubiquitinates p53 in vitro. BRCC36 and BRCC45 are novel components of the complex with sequence homology to a subunit of the signalosome and proteasome complexes. Reconstitution of a recombinant four-subunit complex containing BRCA1/BARD1/BRCC45/BRCC36 revealed an enhanced E3 ligase activity compared to that of BRCA1/BARD1 heterodimer. In vivo, depletion of BRCC36 and BRCC45 by the small interfering RNAs (siRNAs) resulted in increased sensitivity to ionizing radiation and defects in G2/M checkpoint. BRCC36 shows aberrant expression in sporadic breast tumors. These findings identify BRCC as a ubiquitin E3 ligase complex that enhances cellular survival following DNA damage.

BRCA1 Protein↗

PubMed1996

Hepatitis delta antigens enhance the ribozyme activities of hepatitis delta virus RNA in vivo.

The mechanism of regulation for the ribozyme activity of hepatitis delta virus (HDV) RNA in infected cells is unknown. Previously, we developed a direct assay capable of detecting the ribozyme activity of HDV dimer or trimer RNAs in vivo (K.-S. Jeng, A. Daniel, and M. M. C. Lai, J. Virol, 70:2403-2410, 1996). In this study, we used this method to examine the effects of hepatitis delta antigen (HDAg) on the ribozyme activities of HDV RNA in vivo. The HDV multimer cDNAs were cotransfected with plasmids encoding either HDV small delta antigen (SHDAg) or large delta antigen (LHDAg), and the self-cleavage of the primary transcripts from the HDV cDNA was analyzed at day 2 postransfection. The results were as follows. (i) Both HDAgs, particularly LHDAg, enhanced the self-cleavage activity of HDV RNA; however, HDAgs are not required for HDV RNA cleavage. (ii) HDAg could not restore the ribozyme activity of mutant HDV RNAs which have lost the ribozyme function. (iii) The enhancement of ribozyme activity by HDAg does not require HDV RNA replication. (iv) RNA-binding activity of HDAg is required for the enhancement of RNA cleavage. (v) The self-ligation activities of HDV ribozyme also were enhanced by HDAg. These results suggest that HDAg can regulate the cleavage and ligation of HDV RNA during the HDV life cycle.

Cell Line↗

PubMed1990

The induction of vimentin gene expression by sodium butyrate in human promonocytic leukemia U937 cells.

The administration of 1 mM sodium butyrate induced the phenotypic differentiation of human promonocytic leukemia U937 cells, as judged by the expression of cD11b and cD11c antigens, two differentiation-specific surface markers. At the same time, butyrate greatly induced the expression at the mRNA level of the vimentin gene. The increase in the level of this RNA started at 6 h of treatment and reached the maximum at Hour 24. Such an increase was caused at least in part by a stimulation in the rate of gene transcription, as suggested by transcription assays in isolated nuclei. Experiments in the presence of cycloheximide suggested that vimentin induction is probably a direct response to the action of butyrate, not mediated by the prior induction of other gene products. Unlike the case of vimentin, the levels of other RNAs, namely beta-actin, ornithine decarboxylase, and c-myc, were not enhanced, but they decreased at different times of treatment with butyrate. Finally, we observed that butyrate induced also the differentiation of HL60 cells, another human myeloid cell type. Nevertheless, the drug failed to stimulate the expression of vimentin in this cell line.

Butyrates↗

PubMed1999

Cocaine cytotoxicity in hepatocyte cultures from phenobarbital-induced rats: involvement of reactive oxygen species and expression of antioxidant defense systems.

The present study was designed to investigate whether cocaine modifies the production of reactive oxygen species, affects cellular enzyme-mediated antioxidant defense systems and, subsequently, promotes apoptosis and/or necrosis of hepatocytes. Primary cultures of hepatocytes isolated from phenobarbital-induced rats were exposed to cocaine (0-1000 microM) for 24 hr, and cell death (apoptosis or necrosis), antioxidant enzyme activities and mRNA levels, and peroxide generation were determined. Cocaine cytotoxicity by apoptosis was observed by detecting apoptotic nuclei using optic microscopy and by measurement of the hypodiploid peak (<2C) in DNA histograms obtained by flow cytometry. Necrosis was evidenced by lactate dehydrogenase (LDH) leakage, and peroxide production was quantified with 2',7'-dichlorodihydrofluorescein diacetate. Low concentrations of cocaine (less than 100 microM) resulted in an increase in dichlorofluorescein fluorescence, associated with an enhancement in apoptotic cell death and sharp decreases in the enzyme activities and RNAs of catalase and manganese-superoxide dismutase (Mn-SOD). The progressive decrease in peroxide production in cell cultures detected in the range of 250-1000 microM cocaine was associated with increases in LDH leakage and decreases in the percentage of apoptotic cells, accompanied by low levels in catalase and Mn-SOD enzyme activities and mRNAs, without apparent changes in apoptosis. These data indicate that oxygen radicals may contribute directly or indirectly to cocaine-induced apoptosis in cultured hepatocytes. We conclude that, in primary hepatocyte cultures, cocaine-induced cell death by necrosis was dependent on cocaine concentration, while cell death by apoptosis was parallel to peroxide concentration. The down-regulation of the gene expression of antioxidant enzyme systems should be one of the mechanisms involved in cocaine toxicity.

Animals↗

PubMed1996

Restoration of both structure and function to a defective poly(A) site by in vitro selection.

Efficient cleavage and polyadenylation at the human immunodeficiency virus type-1 (HIV-1) poly(A) site requires an upstream 3'-processing enhancer to overcome the suboptimal sequence context of the AAUAAA hexamer. The HIV-1 3'-processing enhancer functions to stabilize the association of the pre-mRNA with cleavage and polyadenylation specificity factor (CPSF), the factor responsible for recognition of the AAUAAA hexamer. Intriguingly, in the absence of the 3'-processing enhancer, CPSF binding and polyadenylation efficiency could be restored to near wild-type levels upon replacement of the 14-nucleotide region immediately 5' of the HIV-1 AAUAAA hexamer (the B segment) by the analogous sequences from the efficient adenovirus L3 poly(A) site. To further investigate the contributions of RNA sequence and structure to poly(A) site recognition, we have used an in vitro selection system to identify B segment sequences that enhance the polyadenylation efficiency of a pre-cleaved RNA lacking a 3'-processing enhancer. The final RNA selection pool was composed of two predominant classes of RNAs. Nuclease probing revealed that the selected sequences restored an RNA conformation that facilitates recognition of the AAUAAA hexamer by CPSF. These results indicate that both the sequence and structural context of the AAUAAA hexamer contribute to poly(A) site recognition by CPSF.

Base Sequence↗

PubMed2006

The scaffolding adapter Gab1 mediates vascular endothelial growth factor signaling and is required for endothelial cell migration and capillary formation.

Vascular endothelial growth factor (VEGF) is involved in the promotion of endothelial cell proliferation, migration, and capillary formation. These activities are mainly mediated by the VEGFR2 receptor tyrosine kinase that upon stimulation, promotes the activation of numerous proteins including phospholipase Cgamma (PLCgamma), phosphatidylinositol 3-kinase (PI3K), Akt, Src, and ERK1/2. However, the VEGFR2-proximal signaling events leading to the activation of these targets remain ill defined. We have identified the Gab1 adapter as a novel tyrosine-phosphorylated protein in VEGF-stimulated cells. In bovine aortic endothelial cells, Gab1 associates with VEGFR2, Grb2, PI3K, SHP2, Shc, and PLCgamma, and its overexpression enhances VEGF-dependent cell migration. Importantly, silencing of Gab1 using small interfering RNAs leads to the impaired activation of PLCgamma, ERK1/2, Src, and Akt; blocks VEGF-induced endothelial cell migration; and perturbs actin reorganization and capillary formation. In addition, co-expression of VEGFR2 with Gab1 mutants unable to bind SHP2 or PI3K in human embryonic kidney 293 cells and bovine aortic endothelial cells mimics the defects observed in Gab1-depleted cells. Our work thus identifies Gab1 as a novel critical regulatory component of endothelial cell migration and capillary formation and reveals its key role in the activation of VEGF-evoked signaling pathways required for angiogenesis.

Adaptor Proteins, Signal Transducing↗

PubMed1991

Alternative modes of self-cleavage by newt satellite 2 transcripts.

Synthetic transcripts of satellite 2 DNA from the newt undergo self-catalyzed cleavage in vitro. In this report we present evidence that there are at least two distinct modes of satellite 2 transcript self-cleavage. In one mode, a single cleavage domain folds into a structure which cleaves at a slow rate. This structure may be analogous to, or a variant of, the 'hammerhead' structure believed to be active during the self-cleavage of a number of infectious plant RNAs. In an alternative mode, multiple cleavage domains interact to cleave at an enhanced rate. The permutation of the repeated satellite 2 sequence determines which of these modes of cleavage will predominate, presumably by influencing the overall conformation of the RNA. We present a model for the self-processing of multimeric satellite 2 transcripts which incorporates both of these modes of self-cleavage.

Animals↗

PubMed1975

Are cytotoxicity and interferon inducing activity of poly(I).poly(C) invariably linked in interferon-treated L cells.

Interferon-treated L cells exhibit a specific enhanced susceptibility to the cytotoxic and interferon inducing activities of double-stranded RNAs such as poly(1). poly(C). These activities remained closely linked through widely varying assay conditions, involving, for example, different time anddosage schedules of poly(1). poly (C),suggesting that there is at least one common step in the mechanisms leading to interferon formation and toxicity in interferon-primed cells exposed to poly(1).poly(C). However, some procedures such as addition of metabolic inhibitors (actinomycin D, cycloheximide) and repeated administration of poly(1).poly(C) suppressed the interferon inducing capacity of poly(1).poly(C) without a concomitant decrease of toxicity. Other procedures such as brief treatment of the cells with interferon or DEAE-dextran permitted full expression of the interferon inducing activity of poly(1).poly(C) without any sign of toxicity. The latter results suggest that the mechanisms underlying interferon production and toxicity of poly(1).poly(C) in interferon-treated L cells diverge from a certain point onward.

Animals↗

PubMed1994

Low efficiency of the 5' nontranslated region of hepatitis A virus RNA in directing cap-independent translation in permissive monkey kidney cells.

To characterize in vivo the translational control elements present in the 5' nontranslated region (5'NTR) of hepatitis A virus (HAV) RNA, we created an HAV-permissive monkey kidney cell line (BT7-H) that stably expresses T7 RNA polymerase and carries out cytoplasmic transcription of uncapped RNA from transfected DNA containing the T7 promoter. The presence of an internal ribosomal entry site (IRES) within the 5'NTR of HAV was confirmed by using BT7-H cells transcribing bicistronic RNAs in which the 5'NTR was placed within the intercistronic space, controlling translation of a downstream reporter protein (bacterial chloramphenicol acetyltransferase). However, translation directed by the 5'NTR in these bicistronic transcripts and in monocistronic T7 transcripts in which the HAV 5'NTR was placed upstream of the chloramphenicol acetyltransferase coding sequence was very inefficient compared with the translation of monocistronic transcripts containing either the IRES of encephalomyocarditis (EMC) virus or a short nonpicornavirus 5' nontranslated leader sequence. A large deletion within the HAV IRES (delta 355-532) eliminated IRES activity in bicistronic transcripts. In contrast, larger deletions within the IRES in monocistronic transcripts (delta 1-354, delta 1-532, delta 1-633, and delta 158-633) resulted in 4- to 14-fold increases in translation. In the latter case, this was most probably due to a shift from IRES-directed translation to translation initiation by 5'-end-dependent scanning. Translation of RNAs containing either the EMC virus IRES or the nonpicornavirus leader was significantly enhanced by cotransfection of the reporter constructs with pEP2A, which directs transcription of RNA containing the EMC virus IRES fused to the poliovirus 2Apro coding region. This 2Apro enhancement of cap-independent translation suggests a greater availability of limiting cellular translation factors following 2Apro-mediated cleavage of the p220 subunit of the eukaryotic initiation factor eIF-4F and subsequent shutdown of 5' cap-dependent translation. In contrast, pEP2A cotransfection resulted in severe inhibition of translation directed by the HAV IRES in either monocistronic or bicistronic transcripts. This inhibition was due to competition from the EMC virus IRES present in pEP-2A transcripts, as well as the expression of proteolytically active 2Apro. 2Apro-mediated suppression of HAV translation was not seen with transcripts containing large deletions in the HAV IRES (delta 158-633, delta 1-532, or delta 1-633). These data suggest that the HAV IRES may have a unique requirement for intact p220 or that it may be dependent on active expression of another cellular translation factor which is normally present in severely limiting quantities.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1999

Ultrastructural localization of beta-actin and amphoterin mRNA in cultured cells: application of tyramide signal amplification and comparison of detection methods.

We describe a nonradioactive preembedding in situ hybridization protocol using digoxigenin-labeled RNA probes and tyramide signal amplification to increase the sensitivity of detection. The protocol is sensitive enough for electron microscopic localization of endogenous messenger RNAs encoding beta-actin and amphoterin. Three visualization methods were compared: diaminobenzidine enhanced by nickel, Nanogold enhanced by silver and gold toning, and fluorescently labeled tyramides. Diaminobenzidine and Nanogold can be used in both light and electron microscopy. The nickel-enhanced diaminobenzidine was the most sensitive visualization method. It is easy to accomplish but a drawback is poor spatial resolution, which restricts its use at high magnifications. Nanogold visualization has considerably better spatial resolution and is therefore recommended for electron microscopy. Fluorescent tyramides, especially TRITC-tyramide, offer a good detection method for fluorescence and confocal microscopy. The methods were used to localize amphoterin and beta-actin mRNAs in motile cells. Both mRNAs were found in the soma and cell processes. In double labeling experiments, beta-actin mRNA localized to filamentous structures that also contained ribosomal proteins. Especially in the cortical cytoplasm, beta-actin mRNA was associated with actin filaments. Direct localization to microtubules was only rarely seen. (J Histochem Cytochem 47:99-112, 1999)

Actins↗

PubMed2026

m6A RNA methylation modulates IFN-γ-stimulated intestinal epithelial cell-intrinsic antiparasitic defense.

N6-methyladenosine (m6A) RNA methylation is one of the most prevalent reversible post-transcriptional RNA modifications and has been recognized as a crucial regulator of host immune responses. Intestinal epithelial cells (IECs) constitute an important component of gastrointestinal mucosal immunity. Interferons (IFNs) play a central role in maintaining intestinal homeostasis, and m6A methylation status influences IFN-mediated cell-intrinsic defense. In this study, we investigated the potential role of m6A RNA modifications in IFN-γ-stimulated IEC-intrinsic defense. We observed significant alterations in the topology of the m6A mRNA methylome in murine IECs following IFN-γ stimulation. A subset of IFN-γ-stimulated immune gene transcripts exhibited increased m6A RNA methylation, including several members of the immunity-related GTPase family M (IRGM) genes. In addition, IFN-γ-responsive long non-coding RNAs may modulate the m6A methylation levels of multiple IFN-γ-stimulated immune transcripts. Enhanced m6A methylation of the Irgm2/3 transcripts was associated with strengthened cell-intrinsic defense against infection by the protozoan parasite Cryptosporidium. Notably, Cryptosporidium infection altered the host m6A mRNA methylome in IECs, thereby counteracting the IFN-γ-mediated defense response. Although the RNA levels of Irgm2/3 genes were upregulated, their m6A RNA methylation levels and protein expression were reduced in infected cells. This effect was associated with host delivery of dsRNAs derived from Cryptosporidium parvum virus 1, a virus harbored in the parasite. Collectively, our findings suggest that m6A methylation of RNA transcripts enhances IFN-γ-mediated IEC-intrinsic antiparasitic defense, while Cryptosporidium has evolved mechanisms to evade this response by suppressing m6A RNA methylation of IFN-γ-stimulated immune genes.

Animals↗

PubMed2001

Enhanced accumulation of coronavirus defective interfering RNA from expressed negative-strand transcripts by coexpressed positive-strand RNA transcripts.

Expression of negative-strand murine coronavirus mouse hepatitis virus (MHV) defective interfering (DI) RNA transcripts in MHV-infected cells results in the accumulation of positive-strand DI RNAs (M. Joo et al., 1996, J. Virol. 70, 5769-5776). However, the expressed negative-strand DI RNA transcripts are poor templates for positive-strand DI RNA synthesis. The present study demonstrated that DI RNA accumulation from the expressed negative-strand DI RNA transcripts in MHV-infected cells was enhanced by the coexpression of complementary RNA transcripts that correspond to the 5' region of positive-strand DI RNA. The positive-strand RNA transcripts corresponding to the 5' end-most 0.7-2.0 kb DI RNA had a similar enhancement effect. The coexpressed positive-strand RNA transcripts lacking the leader sequence or those containing only the leader sequence failed to demonstrate this enhancement effect, demonstrating that the presence of the leader sequence in the coexpressed positive-strand RNA transcripts was necessary, but not sufficient, for the enhancement of DI RNA accumulation from the coexpressed negative-strand DI RNA transcripts. Negative-strand DI RNA transcripts that were coexpressed with the partial-length positive-strand RNA transcripts were no more stable than those expressed alone, suggesting that a higher stability of the expressed negative-strand RNA transcripts was an unlikely reason for the higher DI RNA accumulation in cells coexpressing two complementary DI RNA transcripts. Sequence analyses unexpectedly demonstrated that the leader sequence of the majority of accumulated DI RNAs switched to helper virus derived leader sequence, suggesting that enhancement of DI RNA accumulation was mediated by the efficient utilization of helper virus derived leader sequence for DI RNA synthesis. Furthermore, our data suggested that this leader switching, a type of homologous RNA-RNA recombination, occurred during positive-strand DI RNA synthesis and that MHV positive-strand RNA synthesis mechanism may have a preference toward recognizing double-stranded RNA structures over single-stranded negative-strand RNA to produce positive-strand DI RNAs.

5' Untranslated Regions↗

PubMed2004

Rubella virus capsid protein modulates viral genome replication and virus infectivity.

The structural proteins (SP) of the Togaviridae can be deleted in defective interfering RNAs. The dispensability of viral SP has allowed construction of noninfectious viral expression vectors and replicons from viruses of the Alphavirus and Rubivirus genera. Nevertheless, in this study, we found that the SP of rubella virus (RUB) could enhance expression of reporter genes from RUB replicons in trans. SP enhancement required capsid protein (CP) expression and was not due to RNA-RNA recombination. Accumulation of minus- and plus-strand RNAs from replicons was observed in the presence of SP, suggesting that SP specifically affects RNA synthesis. By using replicons containing an antibiotic resistance gene, we found 2- to 50-fold increases in the number of cells surviving selection in the presence of SP. The increases depended significantly on the amount of transfected RNA. Small amounts of RNA or templates that replicated inefficiently showed more enhancement. The infectivity of infectious RNA was increased by at least 10-fold in cells expressing CP. Moreover, virus infectivity was greatly enhanced in such cells. In other cells that expressed higher levels of CP, RNA replication of replicons was inhibited. Thus, depending on conditions, CP can markedly enhance or inhibit RUB RNA replication.

Animals↗