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Some RISCs are able to directly target the genome by recruiting histone methyltransferases to form heterochromatin at the gene locus, silencing the gene. These RISCs take the form of a RNA-induced transcriptional silencing complex (RITS). The best studied example is with the yeast RITS. [1] [23] [24]
For example, human pre-miRNA 92b adopts a G-quadruplex structure which is resistant to the Dicer mediated cleavage in the cytoplasm. [75] Although either strand of the duplex may potentially act as a functional miRNA, only one strand is usually incorporated into the RNA-induced silencing complex (RISC) where the miRNA and its mRNA target interact.
RNA silencing describes several mechanistically related pathways which are involved in controlling and regulating gene expression. [5] [6] [7] RNA silencing pathways are associated with the regulatory activity of small non-coding RNAs (approximately 20–30 nucleotides in length) that function as factors involved in inactivating homologous sequences, promoting endonuclease activity ...
AGO2 (grey) in complex with a microRNA (light blue) and its target mRNA (dark blue) In humans, there are eight AGO family members, some of which are investigated intensively. However, even though AGO1–4 are capable of loading miRNA, endonuclease activity and thus RNAi-dependent gene silencing exclusively belongs to AGO2.
Gene silencing is the regulation of gene expression in a cell to prevent the expression of a certain gene. [ 1 ] [ 2 ] Gene silencing can occur during either transcription or translation and is often used in research.
A miRNA is expressed from a much longer RNA-coding gene as a primary transcript known as a pri-miRNA which is processed, in the cell nucleus, to a 70-nucleotide stem-loop structure called a pre-miRNA by the microprocessor complex. This complex consists of an RNase III enzyme called Drosha and a dsRNA-binding protein DGCR8.
Trans-acting siRNA (abbreviated "ta-siRNA" or "tasiRNA") are a class of small interfering RNA (siRNA) that repress gene expression through post-transcriptional gene silencing in land plants. [ 1 ] [ 2 ] [ 3 ] Precursor transcripts from TAS loci are polyadenylated and converted to double-stranded RNA, and are then processed into 21-nucleotide ...
Small RNA (sRNA) are polymeric RNA molecules that are less than 200 nucleotides in length, and are usually non-coding. [1] RNA silencing is often a function of these molecules, with the most common and well-studied example being RNA interference (RNAi), in which endogenously expressed microRNA (miRNA) or exogenously derived small interfering RNA (siRNA) induces the degradation of complementary ...