Egyhazi E, Pigon A, Chang J H, Ghaffari S H, Dreesen T D, Wellman S E, Case S T, Olson M O
Department of Medical Cell Biology, Karolinska Institutet, Stockholm, Sweden.
Exp Cell Res. 1988 Oct;178(2):264-72. doi: 10.1016/0014-4827(88)90397-7.
Protein C23 (also called nucleolin or 100-kDa nucleolar protein) is a major nucleolar phosphoprotein involved in ribosome biogenesis. To determine the effects of protein C23 on preribosomal RNA (pre-rRNA) synthesis anti-C23 antiserum was microinjected into nuclei of Chironomus tentans salivary glands. Transcription was measured by incubation of the glands with 32P-labeled RNA precorsors followed by microdissection of nucleoli, RNA extraction, and electrophoretic analyses. Injection of the anti-C23 antibody caused a 2- to 3.5-fold stimulation of 32P incorporation into 38S pre-rRNA. No stimulation was observed in salivary glands injected with preimmune serum or antiserum preabsorbed with protein C23. The stimulatory effect was selective for pre-rRNA as indicated by the lack of stimulation of 32P incorporation into extranucleolar RNA. Injection of the antiserum produced little or no effect on pre-RNA processing as measured by the relative amounts of 32P-labeled intermediate cleavage products of pre-rRNA in stimulated versus control glands. When protein extracts of Chironomus tentans salivary gland nuclei were probed on Western blots with anti-C23 antibody the predominant cross-reacting species was a 110-kDa polypeptide which had an electrophoretic mobility similar to that of protein C23. These results suggest that protein C23 not only is involved in ribosome assembly but also plays a role in regulating the transcription of the preribosomal RNA.
蛋白质C23（也称为核仁素或100 kDa核仁蛋白）是一种参与核糖体生物合成的主要核仁磷蛋白。为了确定蛋白质C23对核糖体前体RNA（pre-rRNA）合成的影响，将抗C23抗血清显微注射到摇蚊唾液腺细胞核中。通过将腺体与32P标记的RNA前体一起孵育，然后对核仁进行显微切割、RNA提取和电泳分析来测量转录。注射抗C23抗体导致32P掺入38S pre-rRNA的量增加了2至3.5倍。在注射了免疫前血清或用蛋白质C23预吸收的抗血清的唾液腺中未观察到刺激作用。如缺乏对32P掺入核仁外RNA的刺激所示，这种刺激作用对pre-rRNA具有选择性。通过测量受刺激腺体与对照腺体中pre-rRNA的32P标记中间切割产物的相对量，发现注射抗血清对pre-RNA加工几乎没有影响。当用抗C23抗体对摇蚊唾液腺细胞核的蛋白质提取物进行蛋白质印迹检测时，主要的交叉反应条带是一种110 kDa的多肽，其电泳迁移率与蛋白质C23相似。这些结果表明，蛋白质C23不仅参与核糖体组装，而且在调节核糖体前体RNA的转录中也发挥作用。
