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mRNA Processing of tRNA Molecules
Most cells have 40 to 50 distinct tRNAs. Transfer RNA’s are derived from longer RNA precursors of enzymatic removal of extranucleotide units from the 5' and 3' ends.
This process involves the action of an endonuclease that recognizes a hairpin loop at the 3' end called RNAse D, which stops two bases at short of CCA terminus, though it later removes these two bases after the 5' end is processed. This enzymatic digestion leaves the molecule called pre-tRNA.
The 5'-P terminus is formed by an enzyme called RNAse P, which removes excess RNA from the 5' end of a precursor molecule by an endonucleolytic cleavage that generates the correct 5' end.
The final modification is to produce the altered bases in the tRNA.
In tRNA, two uridines are converted to pseudo uridine (Ψ), one guanosine to methyl guanosine (MG), one adenine to isopentyladenine (IPA) etc.
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