Poly(A) Signal-Dependent Transcription Termination Occurs through a Conformational Change Mechanism that Does Not Require Cleavage at the Poly(A) Site

摘要: Transcription termination for genes encoding polyadenylated mRNAs requires a functional poly(A) signal (PAS) in the nascent pre-mRNA. Often called PAS-dependent termination, or PADT, it is widely assumed that PAS requirement reflects an obligatory site cleavage termination. Cleavage thought to provide entry 5'-to-3' exonuclease targets RNA polymerase II via transcript-i.e., torpedo model. To assess role of we developed PADT assay using HeLa nuclear extract. Here examine basal mechanism and show at not required PADT. Isolated elongation complexes undergo manner when incubated buffer, absence extract, nucleotides, site. Thus, PADT-proficient conformational change triggers inhibited by α-amanitin, which presumably blocks change.