de la Paz Sánchez María, Torres Alma, Boniotti Maria Beatrice, Gutierrez Crisanto, Vázquez-Ramo Jorge M
Departamento de Bioquímica, Facultad de Química, UNAM, Avenida Universidad y Copilco, México, DF.
Plant Mol Biol. 2002 Sep;50(2):167-75. doi: 10.1023/a:1016029001537.
In higher eukaryotes, the proliferating cell nuclear antigen (PCNA) can be found associated to Cyclin D and Cdk4/6, the kinase complex responsible for cell cycle commitment in response to growth and mitogenic signals. During maize germination, PCNA can be found in protein complexes between 131 and 163 kDa. The sizes of PCNA protein complexes seem to change during germination, so that by the time the S phase starts, a complex of 100 kDa (likely the homotrimeric ring) is the predominant one. PCNA complexes during early germination contain (any of) two PSTAIRE-containing protein kinases of 32 and 36 kDa that readily phosphorylate both histone H1 and maize retinoblastoma-related (RBR) proteins. Kinase activity in PCNA complexes is markedly inhibited by roscovitine and olomoucine, two known Cdk inhibitors. The protein p13(Suc1) only pulls down the 36 kDa PSTAIRE protein. Kinase activity in PCNA immunoprecipitates is maximal during early germination, before the onset of the S-phase, whereas kinase activity associated to pl3(Suc1) reaches a peak later, after the onset of the S-phase. We discuss the physiological repercussions of these findings.
在高等真核生物中，增殖细胞核抗原（PCNA）可与细胞周期蛋白D及细胞周期蛋白依赖性激酶4/6（Cdk4/6）相关联，该激酶复合物负责响应生长和促有丝分裂信号来推动细胞周期进程。在玉米萌发过程中，可在131至163 kDa之间的蛋白质复合物中发现PCNA。PCNA蛋白质复合物的大小在萌发过程中似乎会发生变化，以至于在S期开始时，100 kDa的复合物（可能是同三聚体环）成为主要形式。早期萌发过程中的PCNA复合物含有两种32 kDa和36 kDa的含PSTAIRE蛋白激酶（二者其一），它们能够轻易地磷酸化组蛋白H1和玉米视网膜母细胞瘤相关（RBR）蛋白。PCNA复合物中的激酶活性受到两种已知的Cdk抑制剂——罗可辛和olomoucine的显著抑制。蛋白p13（Suc1）仅能下拉36 kDa的含PSTAIRE蛋白。PCNA免疫沉淀物中的激酶活性在早期萌发期间、S期开始之前最高，而与p13（Suc1）相关的激酶活性在S期开始之后达到峰值。我们讨论了这些发现的生理影响。
