(1)Polyadenylation signal: 5Cap.…… AAUAA、(20 bases).CA UUGUGUUG signal Poly(A) GUrich region cleavage site addition site(1) Polyadenylation signal: 5’ Cap…..…..AAUAA..(20bases).CA………UUGUGUUG signal Poly(A) GUrich region cleavage site addition site