Acheson N H
J Virol. 1981 Feb;37(2):628-35. doi: 10.1128/JVI.37.2.628-635.1981.
The efficiency of processing of polyoma viral RNA and of its export from nucleus to cytoplasm was measured in primary mouse kidney cells by comparing the initial rates of incorporation of [3H]uridine into cytoplasmic and nuclear viral RNA. Appropriate methods of cell fractionation were chosen to maximize yields of cytoplasmic RNA and to minimize leakage of nuclear RNA. Incorporation of [3H]uridine into cellular 4S RNA in the cytoplasm was followed to monitor pool equilibration and maintenance of an excess of radioactive precursor throughout the experimental period. During the early phase of infection (9 to 11 h, in the presence of 5-fluorodeoxyuridine), viral RNA was rapidly and efficiently exported from nucleus to cytoplasm. Viral RNA appeared in the cytoplasm within 6 min of its synthesis, greater than half of the viral RNA synthesized in the nucleus was exported to the cytoplasm. In contrast, during the late phase of infection (28 to 30 h), viral RNA was exported more slowly, appearing in the cytoplasm 12 to 20 min after its synthesis, and much less efficiently-only 5% of late nuclear transcripts was exported. The poor efficiency of processing of late viral RNA may be, in part, a result of (i) the presence in nuclear transcripts of non-mRNA sequences which are removed during processing; (ii) the presence in nuclear transcripts of multiple copies of mRNA sequences, only one of which is incorporated into mature mRNA; and (iii) inefficient polyadenylation of viral nuclear RNA.
通过比较[3H]尿苷掺入细胞质和细胞核病毒RNA的初始速率，在原代小鼠肾细胞中测量了多瘤病毒RNA的加工效率及其从细胞核输出到细胞质的效率。选择了合适的细胞分级分离方法，以最大限度地提高细胞质RNA的产量，并尽量减少细胞核RNA的泄漏。跟踪[3H]尿苷掺入细胞质中的细胞4S RNA，以监测池平衡并在整个实验期间维持过量的放射性前体。在感染的早期阶段（9至11小时，存在5-氟脱氧尿苷），病毒RNA迅速且有效地从细胞核输出到细胞质。病毒RNA在合成后6分钟内出现在细胞质中，细胞核中合成的病毒RNA超过一半输出到细胞质中。相比之下，在感染的后期阶段（28至30小时），病毒RNA输出较慢，在合成后12至20分钟出现在细胞质中，效率也低得多——只有5%的晚期细胞核转录本被输出。晚期病毒RNA加工效率低下可能部分是由于：（i）细胞核转录本中存在在加工过程中被去除的非mRNA序列；（ii）细胞核转录本中存在多个mRNA序列拷贝，其中只有一个被整合到成熟mRNA中；以及（iii）病毒细胞核RNA的聚腺苷酸化效率低下。
