RNAi Triggering Construct Using Endogenous miRNA Initiation
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Solution Overview
Problem
Current methods for inducing targeted RNA interference (RNAi) in vivo require DNA or synthetic nucleic acid molecules with inverted duplications or dual promoters, which are not always efficient and specific, especially for producing siRNAs without exogenous hairpin or foldback structures.
Innovation Solution
The development of RNAi-triggering constructs that utilize endogenous or in vivo-produced miRNAs or siRNAs to initiate siRNA production, guiding cleavage and setting the register for siRNA generation without the need for exogenous hairpin structures, allowing for tissue-specific or cell-specific regulation of target genes or entities like pathogens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DNA or synthetic nucleic acid molecules with inverted duplications or dual promoters are used to induce RNAi, then RNA interference can be triggered, but the efficiency and specificity are insufficient and exogenous hairpin structures are required
Solution Approach 1:
The invention utilizes the cell's own endogenous miRNAs to initiate siRNA production, eliminating the need for exogenous hairpin structures. The system serves itself by using naturally present molecular components (endogenous miRNAs) to trigger the desired RNAi effect, thereby improving reliability while reducing structural complexity
Solution Approach 2:
The invention introduces an intermediary mechanism where endogenous miRNAs act as mediators to initiate the production of siRNAs. These miRNAs guide the cleavage and register setting for siRNA generation, serving as a bridge between the cell's natural RNA processing machinery and the desired targeted gene suppression
2Adaptability or versatility
If exogenous hairpin or foldback structures are used to generate siRNAs, then RNAi can be induced, but tissue-specific or cell-specific regulation is limited
Solution Approach 1:
The invention enables local quality control by allowing different endogenous miRNAs (which are naturally expressed in different tissues or cell types) to initiate siRNA production in specific locations. This provides tissue-specific or cell-specific regulation without requiring complex construct designs, as the specificity is determined by the natural expression patterns of endogenous miRNAs
3Reliability
If conventional RNAi methods are used, then target genes can be suppressed, but off-target effects increase
Solution Approach 1:
By using the cell's own endogenous miRNAs to initiate siRNA production, the system ensures high specificity. The endogenous miRNAs naturally recognize and bind to their specific target sequences with high precision, thereby reducing off-target effects and improving the reliability of target gene suppression
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the specific and predictable formation of siRNAs for the suppression or inactivation of target genes or entities, offering a more efficient and targeted method for RNAi induction without the need for exogenous dsRNA-forming entities, reducing off-target effects and enhancing tissue- and cell-specificity.
Implementation Method 1
Mechanisms that suppress the expression of specific cellular genes, viruses or mobile genetic elements (such as transposons and retroelements) are critical for normal cellular function in a variety of eukaryotes. A number of related processes, discovered independently in plants (Matzke et al., Curr. Opin. Genet. Dev. 11:221-227, 2001), animals (Fire et al., Nature, 391:806-811, 1998) and fungi (Cogoni, Annu. Rev. Microbiol. 55:381-406, 2001), result in the RNA-directed inhibition of gene expression (also known as RNA silencing).
Implementation Method 2
The mature single-stranded miRNA approximately 20-22 nucleotides in length forms by dissociation of the two strands in the duplex, and is selectively incorporated into the RNA-Induced Silencing Complex, or RISC (Zamore, Science, 296:1265-1269, 2002; Tang et al., Genes Dev., 17:49-63, 2003; Xie et al., Curr. Biol. 13:784-789, 2003).
Implementation Method 3
The primary transcripts that eventually form miRNAs are transcribed from non-protein-coding miRNA genes. These transcripts form hairpin structures that are then processed by Dicer (or by Dicer-like activities in plants) to yield small RNA duplexes containing 2-base overhangs at each 3′ end.
Implementation Method 4
In the nucleus, siRNAs also guide heterochromatin-associated histone and DNA methylation, resulting in transcriptional silencing of individual genes or large chromatin domains.
Data Source
AI summary
A method to generate siRNAs in vivo is described, as are constructs and compositions useful in the method. The method does not depend on the use of DNA or synthetic constructs that contain inverted duplications or dual promoters so as to form perfect or largely double-stranded RNA. Rather, the method depends on constructs that yield single-stranded RNA transcripts, and exploits endogenous or in vivo-produced miRNAs or siRNAs to initiate production of siRNAs. The miRNAs or siRNAs guide cleavage of the transcript and set the register for production of siRNAs (usually 21 nucleotides in length) encoded adjacent to the initiation cleavage site within the construct. The method results in specific formation of siRNAs of predictable size and register (phase) relative to the initiation cleavage site. The method can be used to produce specific siRNAs in vivo for inactivation or suppression of one or more target genes or other entities, such as pathogens.