試題詳解

37. Nonsense-mediated decay (NMD) of eukaryotic mRNA. Which of the following descriptions about the NMD is not correct?
(A) NMD is triggered by the presence of premature stop codons.
(B) The exon junction complex (EJC) is bound to the mRNA upstream of each cxon- exon junction.
(C) During splicing, the mRNA is loaded with EJC upstream of each exon-exon junction.
(D) If there is a premature stop codon, the ribosome finishes translating before all of the EJC complexes have been bumnped off the mRNA, then nonsense-mediated decay is triggered by binding of initiation factors (IF) plus Upfl to the remaining EJC.
(E) The next step of NMD is removal of the cap from the mRNA, then the mRNA is degraded from the exposed 5' end.