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:
 * Genomic Imprinting
 * Paramutation
 * Transposon silencing
 * Transgene silencing
 * Transcriptional gene silencing
 * position effect

Post-transcriptional Gene Silencing:
 * post-transcriptional gene silencing
 * RNAi
 * Nonsense mediated decay (NMD)

Cellular components of gene silencing: ribozyme technology and antisense technology are the two approach used in the post transcriptional gene silencing and that is the way to suppress the gene
 * Histones
 * Chromatin and heterochromatin
 * MicroRNA
 * siRNA
 * dsRNA
 * Dicer
 * Transposons