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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 .
For example, in a typical gene a start codon (5′-ATG-3′) is a DNA sequence within the sense strand. Transcription begins at an upstream site (relative to the sense strand), and as it proceeds through the region it copies the 3′-TAC-5′ from the template strand to produce 5′-AUG-3′ within a messenger RNA (mRNA).
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 .
Simple diagram of transcription elongation. One strand of the DNA, the template strand (or noncoding strand), is used as a template for RNA synthesis. As transcription proceeds, RNA polymerase traverses the template strand and uses base pairing complementarity with the DNA template to create an RNA copy (which elongates during the traversal).
Shortly after transcription is initiated in eukaryotes, a pre-mRNA's 5' end is modified by the addition of a 7-methylguanosine cap, also known as a 5' cap. [9] 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 ...
Transcription of mRNAs initiated by viral polymerase using cap snatching. The first step of transcription for some negative, single-stranded RNA viruses is cap snatching, in which the first 10 to 20 residues of a host cell RNA are removed (snatched) and used as the 5′ cap and primer to initiate the synthesis of the nascent viral mRNA. [1]
Unlike the eukaryotic RNA immediately after transcription known as precursor messenger RNA, [1] mature mRNA consists exclusively of exons and has all introns removed. The Maturation of mRNA. Mature mRNA is also called "mature transcript", "mature RNA" or "mRNA". The production of a mature mRNA molecule occurs in 3 steps: [2] [3] Capping of the ...
An open reading frame (ORF) is a reading frame that has the potential to be transcribed into RNA and translated into protein. It requires a continuous sequence of DNA which may include a start codon, through a subsequent region which has a length that is a multiple of 3 nucleotides, to a stop codon in the same reading frame.