RNA as a target of double-stranded RNA-mediated genetic interference in Caenorhabditis elegans

Abstract

Introduction of exogenous double-stranded RNA (dsRNA) into Caenorhabditis elegans has been shown to specifically and potently disrupt the activity of genes containing homologous sequences. In this study we present evidence that the primary interference effects of dsRNA are posttranscriptional. First, we examined the primary DNA sequence after dsRNA-mediated interference and found no evidence for alterations. Second, we found that dsRNAmediated interference with the upstream gene in a polar operon had no effect on the activity of the downstream gene; this finding argues against an effect on initiation or elongation of transcription. Third, we observed by in situ hybridization that dsRNA-mediated interference produced a substantial, although not complete, reduction in accumulation of nascent transcripts in the nucleus, while cytoplasmic accumulation of transcripts was virtually eliminated. These results indicate that the endogenous mRNA is the target for interference and suggest a mechanism that degrades the targeted RNA before translation can occur. This mechanism is not dependent on the SMG system, an mRNA surveillance system in C. elegans responsible for targeting and destroying aberrant messages. We suggest a model of how dsRNA might function in a catalytic mechanism to target homologous mRNAs for degradation.

Knockdown of survivin expression by small interfering RNA reduces the clonogenic survival of human sarcoma cell lines independently of p53

“…[8][9][10][11][12][13][14][15][16] In addition to the use of antisense oligonucleotides and ribozymes, the application of small interfering RNA (siRNA) is an effective way to silence gene transcription. 17,18 Transcription silencing is thought to be a defense strategy that preserves genomes through evolution from attack by double-stranded RNA viruses and transposons. 19,20 Genetic and biochemical studies have confirmed that the mechanisms of gene silencing by siRNAs, cosuppression, and viruses share similarities.…”

Acquisition of inverted GSTM exons by an intron of primate GSTM5 gene

“…The binding of the siRNA triggers several steps for the digestion of mRNA and silences the expression of the target gene. 6,7 The siRNA in this process comes from a stem-loop RNA produced by a microRNA gene. Some of the microRNA genes are located in introns and are associated with their own promoters.…”

“…Processed by a dicer protein, the hairpin eventually becomes a small interfering RNA (siRNA) for RNA interference. 6,7 In other experiments, intronic IRs were shown to affect exon-intron splicing efficiency and determine alternative exon splicing. 8,9 More intriguingly, we found that some intronic LIRs are primate-specific, and probably critical in the evolution toward primates.…”

Régulation de l’expression des séquences répétées et interférence par l’ARN

“…En 1998, Fire et al [14] ont montré qu'il est possible, chez C. elegans, d'inhiber post-transcriptionnellement l'expression d'un gène en injectant dans l'animal des molécules d'ARN double brin ayant une séquence commune avec le gène ciblé [15]. Cette inhibition est spéci-fique puisque seuls les gènes présentant de longues séquences communes avec l'ARN double brin sont éteints.…”