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In molecular biology, the five-prime cap (5′ cap) is a specially altered nucleotide on the 5′ end of some primary transcripts such as precursor messenger RNA.This process, known as mRNA capping, is highly regulated and vital in the creation of stable and mature messenger RNA able to undergo translation during protein synthesis.
The 5′ untranslated region (also known as 5′ UTR, leader sequence, transcript leader, or leader RNA) is the region of a messenger RNA (mRNA) that is directly upstream from the initiation codon. This region is important for the regulation of translation of a transcript by differing mechanisms in viruses, prokaryotes and eukaryotes.
The 5′-untranslated region is the portion of the DNA starting from the cap site and extending to the base just before the AUG translation initiation codon of the main coding sequence. This region may have sequences, such as the ribosome binding site and Kozak sequence , which determine the translation efficiency of the mRNA, or which may ...
5' cap structure. A 5' cap (also termed an RNA cap, an RNA 7-methylguanosine cap, or an RNA m 7 G cap) is a modified guanine nucleotide that has been added to the "front" or 5' end of a eukaryotic messenger RNA shortly after the start of transcription. The 5' cap consists of a terminal 7-methylguanosine residue that is linked through a 5'-5 ...
Capping changes the five prime end of the mRNA to a three prime end by 5'-5' linkage, which protects the mRNA from 5' exonuclease, which degrades foreign RNA. The cap also helps in ribosomal binding. In addition, it represents a unique mark for a correct gene. Therefore, it helps to select the mRNA that is going to be translated.
The PA subunit subsequently cleaves the sequence 10-13 nucleotides from the cap structure via endonuclease activity at the N terminus. [5] The exact cleavage location is dependent both on the distance between the PB2 and the PA of the RdRp (around 50 angstroms or 10-13 nucleotides) and also the sequence of the mRNA.
5' cap structure. Capping is a three-step process that utilizes the enzymes RNA triphosphatase, guanylyltransferase, and methyltransferase. [1] [2] Through a series of three steps, the cap is added to the first nucleotide's 5' hydroxyl group of the growing mRNA strand while transcription is still occurring.
The 5' capping modification is initiated by the addition of a GTP to the 5' terminal nucleotide of the pre-mRNA in reverse orientation followed by the addition of methyl groups to the G residue. [9] 5' capping is essential for the production of functional mRNAs since the 5' cap is responsible for aligning the mRNA with the ribosome during ...