1In what way is transcriptional silencing distinguished from

1.In what way is transcriptional silencing distinguished from transcriptional repression?  

Solution

Both transcriptional silencing and transcriptional repression are ways of transcrition regulation. Transcriptional regulation is the mechanism by which a cell regulates the conversion of DNA to RNA.

Transcriptional silencing usually refers to inhibition of transcription by small interferring RNA species. RNA-induced transcriptional silencing (RITS) is a RNA interference in which short RNA molecules like small interfering RNA (siRNA) bring about the downregulation of transcription of a particular gene sequence. This is usually done by posttranslational modification of histone tails which inturn target the genomic region for heterochromatin formation.  

On the other hand, transcritional repression does not refer to RNA interference. A repressor is a protein that binds to DNA and inhibits the expression of one or more genes, by binding to either the operator or associated silencers. A silencer is a specific DNA sequence element wherein the transcription regulation factors, i.e, repressors binds. It is this repressor which binds to the silencer region of DNA, and hence makes it impossible for RNA polymerase to bind, thus inhibiting transcribing the DNA sequence into RNA. This process is known as transcriptional repression. Transcriptional repressors usually bind to promoters in such a way that impedes subsequent binding of RNA polymerase.