Berger S L, Cooper H L
Biochim Biophys Acta. 1978 Jan 26;517(1):84-98. doi: 10.1016/0005-2787(78)90036-9.
The processing of hnRNA+-poly(A) to mRNA+-poly(A) has been studied in resting lymphocytes from human peripheral blood. In pulse-chase experiments, two types of hnRNA+-poly(A) have been distinguished: the first is labeled predominantly with exogenous radioactive precursors supplied during the pulse, and the second incorporates primarily scavenged labeled precursors made available during a chase incubation. When the disappearance of both types of hnRNA+-poly(A) was quantitatively compared with the appearance of stable and labile mRNA+-poly(A), only 10% of the anticipated cytoplasmic material was actually obtained. Statistically, 90% of the poly(A)-bearing hnRNA molecules processed were degraded. The two types of hnRNA+-poly(A) were found to be functionally different. Pulse-labeled material was processed to poly(A)-bearing mRNA; "chase-labeled" molecules did not leave the nucleus and never served as precursors for cytoplasmic mRNA. The data fit a model in which there are distinct pathways for mRNA precursor- and nonprecursor-hnRNA+-poly(A).
已对来自人外周血的静息淋巴细胞中hnRNA+-聚腺苷酸（poly(A)）加工成mRNA+-聚腺苷酸的过程进行了研究。在脉冲追踪实验中，区分出了两种类型的hnRNA+-聚腺苷酸：第一种主要用脉冲期间提供的外源性放射性前体进行标记，第二种主要掺入在追踪孵育期间可得的清除标记前体。当将这两种类型的hnRNA+-聚腺苷酸的消失与稳定和不稳定的mRNA+-聚腺苷酸的出现进行定量比较时，实际上仅获得了预期细胞质物质的10%。从统计学上看，加工的携带聚腺苷酸（poly(A)）的hnRNA分子中有90%被降解。发现这两种类型的hnRNA+-聚腺苷酸在功能上有所不同。脉冲标记的物质被加工成携带聚腺苷酸（poly(A)）的mRNA；“追踪标记”的分子未离开细胞核，也从未作为细胞质mRNA的前体。这些数据符合一种模型，即mRNA前体和非前体hnRNA+-聚腺苷酸（poly(A)）存在不同的途径。
