Tuel-Ahlgren L, Jun X, Waddick K G, Jin J, Bolen J, Uckun F M
Department of Therapeutic Radiology-Radiation Oncology, University of Minnesota Health Sciences Center, Minneapolis, USA.
Leuk Lymphoma. 1996 Feb;20(5-6):417-26. doi: 10.3109/10428199609052423.
Here we provide experimental evidence that ionizing radiation induces inhibitory tyrosine phosphorylation of the p34cdc2 kinase in human leukemic B-cell precursors. Herbimycin A markedly reduced tyrosine phosphorylation of p34cdc2 in irradiated leukemic B-cell precursors, thereby preventing radiation-induced cell cycle arrest at the G2-M transition checkpoint. Thus, tyrosine phosphorylation is directly responsible for the inactivation of p34cdc2 in irradiated human leukemic B-cell precursors and activation of protein tyrosine kinases is a proximal and mandatory step in radiation-induced G2-arrest arrest at the G2-M checkpoint. Human WEE1 kinase isolated from unirradiated or irradiated leukemic B-cell precursors had minimal tyrosine kinase activity towards p34cdc2. We detected no increase of human WEE1 kinase activity after radiation of leukemic B-cell precursors, as measured by (a) autophosphorylation, (b) tyrosine phosphorylation of a synthetic peptide derived from the p34cdc2 amino-terminal region or (c) recombinant human p34cdc2-cyclin B complex. Thus the signaling pathway leading to inhibitory tyrosine phosphorylation of p34cdc2 and G2-arrest in irradiated human leukemic B-cell precursors functions independent of p49 WEE1 HU and enzymes which augment the tyrosine kinase activity of p49 WEE 1HU.
我们在此提供实验证据，表明电离辐射可诱导人白血病B细胞前体中p34cdc2激酶的抑制性酪氨酸磷酸化。赫伯霉素A可显著降低受辐照白血病B细胞前体中p34cdc2的酪氨酸磷酸化，从而防止辐射诱导的细胞周期在G2-M转换检查点处停滞。因此，酪氨酸磷酸化直接导致受辐照人白血病B细胞前体中p34cdc2的失活，而蛋白酪氨酸激酶的激活是辐射诱导的G2-M检查点处G2期停滞的一个近端且必要的步骤。从未受辐照或受辐照的白血病B细胞前体中分离出的人WEE1激酶对p34cdc2的酪氨酸激酶活性极小。通过（a）自身磷酸化、（b）源自p34cdc2氨基末端区域的合成肽的酪氨酸磷酸化或（c）重组人p34cdc2-细胞周期蛋白B复合物检测，我们未发现白血病B细胞前体辐射后WEE1激酶活性增加。因此，导致受辐照人白血病B细胞前体中p34cdc2抑制性酪氨酸磷酸化和G2期停滞的信号通路独立于p49 WEE1 HU以及增强p49 WEE1 HU酪氨酸激酶活性的酶发挥作用。
