Small dsRNAs induce transcriptional activation in human cells

Abstract

Recent studies have shown that small noncoding RNAs, such as microRNAs and siRNAs, regulate gene expression at multiple levels including chromatin architecture, transcription, RNA editing, RNA stability, and translation. Each form of RNA-dependent regulation has been generally found to silence homologous sequences and collectively called RNAi. To further study the regulatory role of small RNAs at the transcriptional level, we designed and synthesized 21-nt dsRNAs targeting selected promoter regions of human genes E-cadherin, p21 WAF1/CIP1 (p21), and VEGF. Surprisingly, transfection of these dsRNAs into human cell lines caused long-lasting and sequence-specific induction of targeted genes. dsRNA mutation studies reveal that the 5 end of the antisense strand, or ''seed'' sequence, is critical for activity. Mechanistically, the dsRNAinduced gene activation requires the Argonaute 2 (Ago2) protein and is associated with a loss of lysine-9 methylation on histone 3 at dsRNA-target sites. In conclusion, we have identified several dsRNAs that activate gene expression by targeting noncoding regulatory regions in gene promoters. These findings reveal a more diverse role for small RNA molecules in the regulation of gene expression than previously recognized and identify a potential therapeutic use for dsRNA in targeted gene activation.gene regulation ͉ promoter ͉ Argonaute 2

Divergent transcription: A new feature of active promoters

“…Nascent transcripts upstream of promoters have been targeted by siRNAs and, for multiple genes, transfection of a siRNA perfectly complementary to the promoter region upstream of the TSS can alter the transcription level of the downstream gene. [57][58][59][60][61] This process may also be occurring endogenously, suggesting a new regulatory role for cellular short RNAs and the divergent transcripts.…”

RNA Activation

“…A new addition can be made to this category, in the form of activating RNAs, the discovery of which was made serendipitously [ 6 ]. While attempting to silence E-cadherin gene transcription, using small double-stranded RNAs (dsRNAs) in human cells, Li et al [ 7 ] observed that several promoter-targeted dsRNA molecules were able to activate gene and protein expression. A similar event was also confi rmed independently by Janowski et al .…”

AID in reprogramming: Quick and efficient

“…In heterokaryons, it is possible that certain RNA species may activate expression of endogenous genes encoding the known reprogramming factors. Although small RNAs have normally been known to silence gene expression, recent studies surprisingly revealed that certain RNAs can also induce potent transcriptional activation of endogenous genes by targeting gene promoters [8,9]. If specific RNAs that target the promoter regions of the pluripotency genes can be identified, they can be used to activate these genes.…”