Stokke T, Erikstein B K, Smedshammer L, Boye E, Steen H B
Department of Biophysics, Norwegian Radium Hospital, Montebello, Oslo.
Exp Cell Res. 1993 Jan;204(1):147-55. doi: 10.1006/excr.1993.1019.
The product of the retinoblastoma susceptibility gene (pRB) exerts its growth-regulatory effects during the G1 phase of the cell cycle, where all pRB present has been assumed to be in the underphosphorylated form. We demonstrate here that pRB is underphosphorylated and firmly bound in the nucleus only in early G1 phase. All G0 cells contain bound, underphosphorylated pRB. The duration of the cell cycle and of the G1 phase seems to be determined by the time during which pRB is underphosphorylated and bound in the nucleus. The observed time lag between the phosphorylation and release of pRB in the G1 phase and entry into S phase was 6.5 h and independent of the G1 transit time. The data suggest that pRB is not directly involved in initiation of DNA replication.
视网膜母细胞瘤易感基因（pRB）的产物在细胞周期的G1期发挥其生长调节作用，在此阶段，所有存在的pRB都被认为处于低磷酸化形式。我们在此证明，pRB仅在G1早期处于低磷酸化状态并牢固地结合在细胞核中。所有G0细胞都含有结合的、低磷酸化的pRB。细胞周期和G1期的持续时间似乎由pRB在细胞核中处于低磷酸化和结合状态的时间决定。在G1期观察到的pRB磷酸化和释放与进入S期之间的时间间隔为6.5小时，且与G1期的过渡时间无关。数据表明，pRB不直接参与DNA复制的起始。
