The nucleus-localized C2 protein of Tomato yellow leaf curl virus-China (TYLCV-C) is an active suppressor of posttranscriptional gene silencing (PTGS). Consistently, infection with TYLCV-C resulted in PTGS arrest in plants. The C2 protein possesses a functional, arginine-rich nuclear localization signal within the basic amino acid-rich region (17)KVQHRIAKKTTRRRR(31). When expressed from potato ...

Antisense oligodeoxynucleotides (AONs) and short interfering RNAs (siRNAs) effect posttranscriptional gene silencing (PTGS) by hybridizing to an mRNA and then directing its cleavage. To understand the constraints that mRNA structure imposes on AON- vs. siRNA-mediated PTGS, AON- and siRNA-mediated cleavage of defined mRNA structures was monitored in Drosophila embryo whole-cell lysates. We obser...

Post-transcriptional gene silencing (PTGS) makes possible new approaches for studying the various steps of the viral cycle. Plus-strand RNA viruses appear to be attractive targets for small interfering RNAs (siRNAs), as their genome functions as both mRNA and replication template. PTGS creates an alternative to classic reverse genetics for viruses with either negative-strand or double-stranded ...

Epigenetic regulation of gene expression is a heritable change in gene expression that cannot be explained by changes in gene sequence. It can result in the repression or activation of gene expression and is therefore referred to as gene silencing or gene activation respectively. Until the end of the 1980s, only modifications of DNA or protein that lead to transcriptional repression or activati...

Post-transcriptional gene silencing (PTGS) in plants results from the action of a mechanism that surveys the RNAs in a cell and specifically degrades those it perceives as alien. The alien RNAs can be doublestranded (ds) or single-stranded (ss) molecules that have homology to dsRNA present in the cell. Most plant viruses have RNA genomes that replicate to produce plus and minus sense RNAs, with...

Abbreviations: attE: attacin E gene ELISA: Enzyme Linked Immunosorbent Assay gusA: β-glucuronidase gene GUS: glucuronidase nos: nopaline synthase gene nptII: neomycin phosphotransferase II gene NPTII: neomycin phosphotransferase II protein PCR: polymerase chain reaction PTGS: post-transcriptional gene silencing RNA: ribonucleic acid RT-PCR: reverse transcription PCR T-DNA: transfer DNA TGS: tra...

Geminiviruses are single-stranded circular DNA viruses causing leaf curl disease in papaya crop. Post-Transcriptional Gene Silencing (PTGS), also known as RNAi, acts as a natural antiviral defence mechanism and plays a role in genome maintenance and development in plants. PTGS suppression by viruses makes the plant RNA silencing machinery inefficient. Three geminiviral genes namely AV2, AC2 and...

Individual genetic background together with environmental effects are thought to be behind many human complex diseases. A number of genetic variants, mainly single nucleotide polymorphisms (SNPs), have been shown to be associated with various pathological and inflammatory conditions, representing potential therapeutic targets. Prostaglandins (PTGs) and leukotrienes (LTs) are eicosanoids derived...

In plants, small interfering RNAs (siRNAs) with sequence homology to transcribed regions of genes can guide the sequence-specific degradation of corresponding mRNAs, leading to posttranscriptional gene silencing (PTGS). The current consensus is that siRNA-mediated PTGS occurs primarily in the cytoplasm where target mRNAs are localized and translated into proteins. However, expression of an inve...

Plants employ post-transcriptional gene silencing (PTGS) as an antiviral defense response. In this mechanism, viral-derived small RNAs are incorporated into the RNA-induced silencing complex (RISC) to guide degradation of the corresponding viral RNAs. ARGONAUTE1 (AGO1) is a key component of RISC: it carries the RNA slicer activity. As a counter-defense, viruses have evolved various proteins tha...