Which of the following statements is not true regarding 5' cap of mRNA :
Eukaryotic mRNA The 5' terminal is "capped" by a 7-methylguanosine triphosphate Linked to an adjacent 2'-O-methyl ribonucleoside at its 5'-hydroxyl through the three phosphates. Contain internal 6-methyladenine and 2'-O-ribose-methylated nucleotides. The cap is involved in : Recognition of mRNA by the translation machinery Stabilize the mRNA by preventing the nucleolytic attack by 5'-exonucleases. Post-transcriptional modification of mRNA include the 7-methylguanosine capping, splicing, and Polyadenylation forming Poly A tail 5' "Capping":This is the first of the processing reactions for pre mRNA. The cap is a 7-methylguanosine attached "backward" to the 5'-terminal end of the mRNA, forming an unusual 5'-5' triphosphate linkage. Poly-A tail is added after transcription by the nuclear enzyme, polyadenylate polymerase, using ATP as the substrate. These tails help stabilize the mRNA, facilitate its exit from the nucleus, and aid in translation. Maturation of eukaryotic mRNA usually involves the removal of introns & joining of exons together to form the mature mRNA. The process of removing introns and joining exons is called splicing. snRNA facilitates the removal of introns by forming base pairs with the consensus sequences at each end of the intron.
5' terminal of mRNA is capped by 7-methylguanosine triphosphate
5' cap contains 2'-O-methyl ribonucleoside adjacent to it.
Cap is attached to the 5' end of mRNA through 5' to 3' phosphodiester bond.
7-methylguanosine is attached to mRNA through three intervening phosphate groups
Molecular Biology