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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 .
When translationally repressed or marked for decay by various mechanisms the 5' cap is bound by the mRNA decapping enzyme DCP2. A host of proteins accompany it including UPF1, UPF2, UPF3A, Dcp1, Dhh1, XRN1, and others. The decapping enzyme removes the 5' cap leading to destruction of the message. [4]
Activating transcription factor 4 (tax-responsive enhancer element B67), also known as ATF4, is a protein that in humans is encoded by the ATF4 gene. [5] [6] Function
Cap-snatching also explains why some viral mRNA have 5’ terminal extensions of 10-20 nucleotides that are not encoded for in the genome. Examples of viruses that engage in cap-snatching include influenza viruses (Orthomyxoviridae), Lassa virus (Arenaviridae), hantaan virus (Hantaviridae) and rift valley fever virus (Phenuiviridae).
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 ...
Last, RNA methyltransferase transfers a methyl group to the guanosine cap to yield 7-methylguanosine cap that is attached to the 5' end of the transcript. [ 1 ] [ 3 ] [ 4 ] [ 5 ] These three enzymes, collectively called the capping enzymes, are only able to catalyze their respective reactions when attached to RNA polymerase II, an enzyme ...
In particular, eIF1 dissociation from the 40S subunit is considered to be a key step in start codon recognition. [ 4 ] eIF1 and eIF1A are small proteins (13 and 16 kDa, respectively in humans) and are both components of the 43S PIC . eIF1 binds near the ribosomal P-site , while eIF1A binds near the A-site , in a manner similar to the ...
In general, there are 4 main cellular compartments, they are: The nuclear compartment comprising the nucleus; The intercisternal space which comprises the space between the membranes of the endoplasmic reticulum (which is continuous with the nuclear envelope) Organelles (the mitochondrion in all eukaryotes and the plastid in phototrophic ...