Gene Silencing : A brief review

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 Gene Silencing : A brief review 

Controlling the expression of genes is a phenomenon known as gene silencing. There are two ways to regulate gene expression: translation and transcription.

Gene silencing and gene knockdown, in which gene expression is decreased, are quite similar. It must be distinguished from gene knockout, which is the total removal of a gene from the genome.


Silencing of Transcriptional Genes
Transcriptional gene silencing is the term used to describe the silencing of genes at the transcriptional level. It is a process of alteration in which the machinery of transcription is disabled. The techniques for transcriptional gene silencing are as follows:

Mendelian inheritance is the basis for the epigenetic approach known as genomic imprinting. The genes that children acquire from their parents determine how those genes are expressed in them. Histone modification or DNA methylation silences the gene, which is passed down unchanged to the progeny.
Paramutation is the process through which two alleles of a gene interact to modify one of them in a way that is heritable through histone modification or DNA methylation.

Position Effect: As the name implies, a gene's expression can be changed by translocating it to a different site on a chromosome.
RNA Directed DNA Methylation: To silence genes, non-coding RNA molecules direct the methylation of certain DNA regions.
Transposable or jumping elements are placed in between genes to suppress their effects through a process known as transposon silencing. Mutations and genetic instability are the results.

Transgene silencing: To lessen the expression of a gene, a transgene is injected into the genome.

Silencing of Post-transcriptional Genes
Post-transcriptional gene silencing is the term used to describe the silencing of genes at the translational stage. The techniques for post-transcriptional gene silencing are as follows:

Short double-stranded RNA sequences (dsRNA) are inserted into the genome during a process known as "RNA interference," or "RNA interference." These dsRNA attach to the functioning mRNA and block its function.

Nonsense Mediated Decay: This is a surveillance technique that finds nonsense mutations in mRNA and silences the translation of proteins. 

Through the breakdown of their cognate mRNA, double-stranded RNA selectively suppresses the expression of homologous genes through a process known as RNA interference (RNAi). Thus, silence is a phenomena that occurs after transcription.

The double-stranded RNA's sequence determines the very specific genetic silencing that RNAi produces.

RNAi in animals and post-transcriptional gene silencing in plants and fungus share a mechanistic relationship.

An enzyme known as the RNA-induced silencing complex, or RISC, is a multi-component nuclease that destroys mRNA.

After being processed, the input double-stranded RNA is reduced to roughly 22 nucleotides, which are then integrated into the RISC. In this instance, they serve as "guide RNAs," giving the nuclease target specificity.

 

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