Cleavage and polyadenylation of Intronless Pre-mRNA

The nuclear poly(A) binding protein (PABPN1), which binds the growing poly(A) tails once it has reached a length of about ten nucleotides. Stimulation of poly(A) polymerase by both CPSF and PABPN1 is synergistic and results in processive elongation of the RNA (the polymerase adds AMP residues without dissociating from the RNA). The processive reaction is terminated when the tail has reached a length of about 250 nucleotides.

核多聚(A)结合蛋白(PABPN1)一旦多聚(A)尾部长度达到约十个核苷酸，便与之结合。CPSF与PABPN1共同刺激多聚(A)聚合酶，其协同作用导致RNA(聚合酶在未从RNA解离的情况下添加AMP残基)的连续延长。当尾部长度达到约250个核苷酸时，连续反应即告终止。