Transcriptional start site

Definition

The transcriptional start site (TSS) is the location on DNA where RNA polymerase begins synthesizing RNA. It marks the first nucleotide of the transcribed RNA molecule.

5 Must Know Facts For Your Next Test

1. The TSS is usually denoted as +1 in nucleotide numbering.
2. In prokaryotes, the TSS is often situated downstream of promoter regions such as the -10 and -35 elements.
3. The efficiency of transcription initiation can be influenced by sequences surrounding the TSS.
4. Sigma factors in prokaryotes help RNA polymerase recognize and bind to the promoter region near the TSS.
5. Mutations near or at the TSS can significantly impact gene expression levels.

Review Questions

Related terms

Promoter:

A DNA sequence upstream of a gene that facilitates binding of RNA polymerase to initiate transcription.

Sigma Factor: A protein that associates with RNA polymerase to facilitate its binding to specific promoters in prokaryotes.

RNA Polymerase: The enzyme responsible for synthesizing RNA from a DNA template during transcription.