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. Gene silencing occurs when RNA is unable to make a protein during translation.

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 or blocked. The destruction of the mRNA prevents translation to form an active gene product (in most cases, a protein). The blocking of the gene occurs through the activity of silencers, which bind to repressor regions. 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.

Genes may be silenced by DNA methylation during meiosis, as in the filamentous fungus Neurospora crassa.

Specific studies of gene silencing

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

Transcriptional Gene Silencing:

• Genomic Imprinting
• Paramutation
• Transposon silencing
• Transgene silencing
• Transcriptional gene silencing
• position effect
• RNA-directed DNA methylation

Post-transcriptional Gene Silencing:

• RNA interference
• Nonsense mediated decay

Meiotic gene silencing:

• Transvection
• Meiotic silencing of unpaired DNA

Cellular components of gene silencing:

• Histones
• Chromatin and heterochromatin
• MicroRNA
• siRNA
• dsRNA
• Dicer
• Transposons

Ribozymes, siRNA and antisense technologies such as Morpholino or PNA oligos are experimental approaches used to post-transcriptionally silence targeted genes of interest.

External links

• RNAiAtlas - database of siRNA libraries and their target analysis results
• Science project: Transgenic apple varieties Approaches to preventing outcrossing – possible effects on micro-organisms
• Gene silencing at the US National Library of Medicine Medical Subject Headings (MeSH)
• Research project: New Cost-effective method for gene silencing
• van Leeuwen F, Gottschling DE. (2002). "Assays for gene silencing in yeast.". Methods Enzymol. 350: 165–86. doi:10.1016/S0076-6879(02)50962-9. PMID 12073311.