Difference between Transcriptional and Post-transcriptional Gene Silencing

Gene silencing is the phenomenon of controlling the expression of genes. The expression of genes can be controlled at two levels: translation and transcription.

Gene silencing is quite similar to gene knockdown where the expression of genes is reduced. However, it should not be confused with gene knockout which is a complete elimination of genes from the genome.

Transcriptional Gene Silencing

The silencing of genes at the transcriptional level is referred to as transcriptional gene silencing. It is a modification procedure where the transcriptional machinery is rendered inaccessible. Following are the methods of transcriptional gene silencing:

  • Genomic Imprinting: It is an epigenetic technique that follows Mendelian inheritance. The expression of genes in the offspring depends on the inheritance from their parents. The gene is silenced by DNA methylation or histone modification and it is inherited as it is to the offspring.
  • Paramutation: It is a procedure where two alleles of a gene interact with each other to produce heritable changes in one of them by DNA methylation or histone modification. The allele that is silenced is called paramutable and the allele that silences is called the paramutagenic.
  • Position Effect: As the name suggests, the expression of a gene is altered by changing its position in the chromosome by translocation.
  • RNA Directed DNA Methylation: Non-coding RNA molecules guide the DNA methylation of DNA sequences to silence the genes.
  • Transposon Silencing: Transposable or jumping elements get inserted between the genes and silence its effect. It causes genomic instability and mutations.
  • Transgene Silencing: A transgene is inserted into the genome to reduce the expression of genes.

Post-transcriptional Gene Silencing

The silencing of genes at the level of translation is referred to as post-transcriptional gene silencing. Following are the methods of post-transcriptional gene silencing:

  • RNAi (RNA interference): It is a procedure where short double-stranded RNA sequences (dsRNA) are introduced into the genome that bind to the functional mRNA and silence its effect.
  • Nonsense Mediated Decay: It is a surveillance method where mRNA with nonsense mutations are detected that leads to silencing of the protein translation.

Transcriptional vs Post-transcriptional Gene Silencing

Transcriptional Gene Silencing

Post-transcriptional Gene Silencing

Definition

The silencing of gene at the transcriptional level is referred to as transcriptional gene silencing.

The silencing of genes at translational levels is referred to as post-transcriptional gene silencing.

Mechanism

RNA synthesis is decreased because of the methylation of the promoter.

It involves sequence-specific RNA degradation by formation of dsRNA.

Promoter

The promoter is silenced.

The promoter is active.

Location

It happens in the nuclei.

It happens in the cytoplasm.

Level of the Event

It happens at transcriptional level.

It happens at translational level.

Methylation

The promoter region is methylated.

The coding region is methylated.

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Frequently Asked Questions

What causes transcriptional silencing?

Histone modifications cause transcriptional gene silencing.

Is gene knockdown the same as gene silencing?

Gene knockdown is quite similar to gene knockdown as both involve silencing the effects of genes and not total gene elimination.

What is an example of gene silencing?

Flavr Savr tomatoes are an example of gene silencing. Tomatoes tend to have a short shelf life because they ripe very soon. To slow down the ripening process, the gene silencing method was introduced in their genome.

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