5' UTR

5' Untranslated Region (5' UTR)

The 5' Untranslated Region (5' UTR) is a region of an mRNA molecule that is directly upstream from the start codon. This region is crucial for the regulation of translation and plays a significant role in the control of gene expression.

Structure

The 5' UTR is part of the exon of a gene and is transcribed into mRNA but is not translated into protein. It is located between the 5' cap and the start codon of the mRNA. The length of the 5' UTR can vary significantly between different mRNAs, ranging from a few nucleotides to several hundred nucleotides.

Function

The 5' UTR contains various regulatory elements that influence the initiation of translation. These elements can include:

• **Ribosome binding sites**: Sequences that facilitate the binding of the ribosome to the mRNA.
• **Upstream open reading frames (uORFs)**: Short sequences that can regulate the translation of the main coding sequence.
• **Internal ribosome entry sites (IRES)**: Sequences that allow for translation initiation in a cap-independent manner.
• **Secondary structures**: Such as stem-loops that can affect the accessibility of the ribosome to the mRNA.

Role in Gene Expression

The 5' UTR is involved in the regulation of gene expression at the translational level. It can influence the efficiency of translation initiation, which in turn affects the amount of protein produced from a given mRNA. Variations in the 5' UTR, such as mutations or alternative splicing, can lead to changes in protein expression and are associated with various diseases.

Clinical Significance

Mutations in the 5' UTR can lead to diseases by affecting the translation of important proteins. For example, mutations that create or disrupt upstream open reading frames (uORFs) can lead to diseases such as cancer or genetic disorders.

Also see

• 3' UTR
• mRNA
• Translation (biology)
• Gene expression
• Ribosome