Gorbsky G J, Ricketts W A
Department of Anatomy and Cell Biology, University of Virginia, Charlottesville.
J Cell Biol. 1993 Sep;122(6):1311-21. doi: 10.1083/jcb.122.6.1311.
A phosphorylated epitope is differentially expressed at the kinetochores of chromosomes in mitotic cells and may be involved in regulating chromosome movement and cell cycle progression. During prophase and early prometaphase, the phosphoepitope is expressed equally among all the kinetochores. In mid-prometaphase, some chromosomes show strong labeling on both kinetochores; others exhibit weak or no labeling; while in other chromosomes, one kinetochore is intensely labeled while its sister kinetochore is unlabeled. Chromosomes moving toward the metaphase plate express the phosphoepitope strongly on the leading kinetochore but weakly on the trailing kinetochore. This is the first demonstration of a biochemical difference between the two kinetochores of a single chromosome. During metaphase and anaphase, the kinetochores are unlabeled. At metaphase, a single misaligned chromosome can inhibit further progression into anaphase. Misaligned chromosomes express the phosphoepitope strongly on both kinetochores, even when all the other chromosomes of a cell are assembled at the metaphase plate and lack expression. This phosphoepitope may be involved in regulating chromosome movement to the metaphase plate during prometaphase and may be part of a cell cycle checkpoint by which the onset of anaphase is inhibited until complete metaphase alignment is achieved.
一种磷酸化表位在有丝分裂细胞中染色体的动粒上差异表达，可能参与调节染色体运动和细胞周期进程。在前期和早中期，该磷酸化表位在所有动粒上均一表达。在中期，一些染色体的两个动粒均显示强标记；另一些则显示弱标记或无标记；而在其他染色体中，一个动粒被强烈标记，而其姐妹动粒未被标记。向中期板移动的染色体在前导动粒上强烈表达该磷酸化表位，而在拖尾动粒上表达较弱。这是首次证明单条染色体的两个动粒之间存在生化差异。在中期和后期，动粒无标记。在中期，一条未正确排列的染色体会抑制进一步进入后期。即使细胞中的所有其他染色体都已排列在中期板上且无表达，未正确排列的染色体在其两个动粒上仍强烈表达该磷酸化表位。这种磷酸化表位可能在前期参与调节染色体向中期板的运动，并且可能是细胞周期检查点的一部分，通过该检查点抑制后期的开始直至实现完全的中期排列。
