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Information about Gene Silencing

Gene silencing is a general term describing epigenetic processes of gene regulation. The term gene silencing is generally used to describe the "switching off" of a gene by a mechanism other than genetic modification. That is, a gene which would be expressed (turned on) under normal circumstances is switched off by machinery in the cell.

Genes are regulated at either the transcriptional or post-transcriptional level.

Transcriptional gene silencing is the result of histone modifications, creating an environment of heterochromatin around a gene that makes it inaccessible to transcriptional machinery (RNA polymerase, transcription factors, etc.).

Post-transcriptional gene silencing is the result of mRNA of a particular gene being destroyed. The destruction of the mRNA prevents translation to form an active gene product (in most cases, a protein). A common mechanism of post-transcriptional gene silencing is RNAi.

Both transcriptional and post-transcriptional gene silencing are used to regulate endogenous genes. Mechanisms of gene silencing also protect the organism's genome from transposons and viruses. Gene silencing thus may be part of an ancient immune system protecting from such infectious DNA elements.

Specific studies of gene silencing

There are several more terms related to specific topics of gene silencing:

Transcriptional Gene Silencing: Post-transcriptional Gene Silencing: Cellular components of gene silencing:

External links

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Biochemistry: regulation of gene expression
Epigenetics is a term in biology used today to refer to features such as chromatin and DNA modifications that are stable over rounds of cell division but do not involve changes in the underlying DNA sequence of the organism.
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Regulation of gene expression (or gene regulation) refers to the cellular control of the amount and timing of changes to the appearance of the functional product of a gene.
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Genetic engineering, recombinant DNA technology, genetic modification/manipulation (GM) and gene splicing are terms that are applied to the direct manipulation of an organisms genes.
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For a non-technical introduction to the topic, see .
A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions.
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Transcription is the process through which a DNA sequence is enzymatically copied by an RNA polymerase to produce a complementary RNA. So to say, it is the transfer of genetic information from DNA into RNA.
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Translation is the second process of protein biosynthesis (part of the overall process of gene expression). Translation occurs in the cytoplasm where the ribosomes are located. Ribosomes are made of a small and large subunit which surrounds the mRNA.
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histones are the chief protein components of chromatin. They act as spools around which DNA winds, and they play a role in gene regulation.

Classes

Six major histone classes are known:
* H1 (sometimes called the linker histone; also related to Histone H5.

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Heterochromatin is a tightly packed form of DNA. Its major characteristic is that transcription is limited.

Structure

Chromatin is found in two varieties: euchromatin and heterochromatin.
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RNA polymerase (RNAP or RNApol) is an enzyme that makes an RNA copy of a DNA or RNA template. In cells, RNAP is needed for constructing RNA chains from DNA genes, a process called transcription.
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Please [improve the article] or discuss this issue on the talk page. This article has been tagged since December 2006.
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Messenger Ribonucleic Acid (mRNA) is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes.
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Translation is the interpretation of the meaning of a text in one language (the "source text") and the production, in another language, of an equivalent text (the "target text," or "translation") that communicates the same message.
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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RNAI is a non-coding RNA that is an antisense repressor of the replication of some E. coli plasmids, including ColE1. Plasmid replication is usually initiated by RNAII, which acts as a primer by binding to its template DNA.
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Transposons are sequences of DNA that can move around to different positions within the genome of a single cell, a process called transposition. In the process, they can cause mutations and change the amount of DNA in the genome.
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Genomic imprinting is a genetic phenomenon by which certain genes are expressed in a parent of origin-specific manner. Forms of genomic imprinting have been demonstrated in insects, mammals and flowering plants.
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Paramutation, in epigenetics, is an interaction between two alleles of a single locus, resulting in a heritable change of one allele that is induced by the other allele. Paramutation violates Mendel’s first law, which states that in the process of the formation of the gametes
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Position effect is the effect on the expression of a gene when its location in a chromosome is changed, often by translocation. This has been well described in Drosophila with respect to eye color and is known as position effect variegation (PEV).
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Post transcriptional gene silencing (PTGS) is a mechanism for sequence-specific RNA degradation in plants similar to RNA interference in other organisms.

The process was described first in transgenic Petunia.
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RNAI is a non-coding RNA that is an antisense repressor of the replication of some E. coli plasmids, including ColE1. Plasmid replication is usually initiated by RNAII, which acts as a primer by binding to its template DNA.
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Nonsense mediated decay (NMD) is a cellular mechanism of mRNA surveillance to detect nonsense mutations and prevent the expression of truncated or erroneous proteins. NMD is triggered by exon-junction complexes (EJC), that have been formed during pre-RNA processing, being
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histones are the chief protein components of chromatin. They act as spools around which DNA winds, and they play a role in gene regulation.

Classes

Six major histone classes are known:
* H1 (sometimes called the linker histone; also related to Histone H5.

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Chromatin is the complex of DNA and protein that makes up chromosomes. It is found inside the nuclei of eukaryotic cells, and within the nucleoid in prokaryotes.[1] The nucleic acids are in the form of double-stranded DNA (a double helix).
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Heterochromatin is a tightly packed form of DNA. Its major characteristic is that transcription is limited.

Structure

Chromatin is found in two varieties: euchromatin and heterochromatin.
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microRNAs (miRNA) are single-stranded RNA molecules of about 21-23 nucleotides in length, which regulate gene expression. miRNAs are encoded by genes that are transcribed from DNA but not translated into protein (non-coding RNA); instead they are processed from primary
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Sirna can mean:
  • In Irish history: Sírna
  • In biology: Small interfering RNA (siRNA)

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Dicer is a ribonuclease in the RNase III family that cleaves double-stranded RNA (dsRNA) and pre-microRNA (miRNA) into short double-stranded RNA fragments called small interfering RNA (siRNA) about 20-25 nucleotides long, usually with a two-base overhang on the 3' end.
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Transposons are sequences of DNA that can move around to different positions within the genome of a single cell, a process called transposition. In the process, they can cause mutations and change the amount of DNA in the genome.
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