Diez J, Brawerman G
Proc Natl Acad Sci U S A. 1974 Oct;71(10):4091-5. doi: 10.1073/pnas.71.10.4091.
Chinese hamster and mouse sarcoma 180 ascites cells, treated with high levels of actinomycin D, still carry out limited poly(A) synthesis. The residual activity, which consists of poly(A) chain extension in the cytoplasm as well as in the nucleus, is essentially insensitive to cordycepin. Nuclear polyadenylation proceeds linearly and involves the gradual extension of unusually long poly(A) sequences. Cytoplasmic poly(A) labeling is initially more rapid than in the nucleus, but levels off within 5-10 min. It consists of addition of seven to eight AMP residues to the poly(A) sequences in preexisting mRNA molecules. The levelling off can be accounted for by a rapid turnover of the extremity of the poly(A) chain in the mRNA. Cytoplasmic poly(A) chain extension can be detected in cells not subjected to the actinomycin treatment. The rate of this process is of the same order of magnitude as that of new poly(A) transfer from nucleus to cytoplasm. It could serve to control the length of the poly(A) sequence in mRNA.
用高剂量放线菌素D处理的中国仓鼠和小鼠肉瘤180腹水细胞仍能进行有限的多聚腺苷酸（poly(A)）合成。残余活性包括细胞质和细胞核中的多聚腺苷酸链延伸，对虫草素基本不敏感。细胞核中的多聚腺苷酸化呈线性进行，涉及异常长的多聚腺苷酸序列的逐渐延伸。细胞质多聚腺苷酸标记最初比细胞核中的更快，但在5-10分钟内趋于平稳。它包括在预先存在的mRNA分子中的多聚腺苷酸序列上添加七到八个AMP残基。这种平稳可以通过mRNA中多聚腺苷酸链末端的快速周转来解释。在未接受放线菌素处理的细胞中可以检测到细胞质多聚腺苷酸链延伸。这个过程的速率与新的多聚腺苷酸从细胞核转移到细胞质的速率处于同一数量级。它可能用于控制mRNA中多聚腺苷酸序列的长度。
