Granick S, Granick D
J Cell Biol. 1971 Dec;51(3):636-42. doi: 10.1083/jcb.51.3.636.
The round nucleoli of chick embryo myoblasts, when grown in a culture medium devoid of arginine, unravel in several days into 5-20 micro long, beaded strands termed nucleolar necklaces (NN). Addition of arginine reverses this change. The NN contain protein, RNA, and traces of DNA as determined cytochemically by enzyme digestion and by acridine-orange fluorescent staining. When a cell containing the beaded strand is treated with agents, such as actinomycin D, that prevent rRNA polymerase action, the strand collapses and condenses into a small dense nucleolus with segregated regions of ribonucleoprotein (RNP) and deoxyribonucleoprotein (DNP). The properties of the NN appear to resemble those of the nucleolar necklaces of amphibian oocytes. Cycloheximide or puromycin inhibition of general protein synthesis does not lead to NN formation. We suggest that NN formation during arginine starvation may be a result of a singular depletion of some rapidly turning over, arginine-rich proteins that normally attach to ribosomal RNA precursor molecules during their synthesis in the processing towards maturation of the ribosomes.
鸡胚成肌细胞的圆形核仁，在不含精氨酸的培养基中生长时，几天内会解聚成5 - 20微米长的串珠状链，称为核仁项链（NN）。添加精氨酸可逆转这种变化。通过酶消化和吖啶橙荧光染色进行细胞化学测定，NN含有蛋白质、RNA和微量DNA。当含有串珠状链的细胞用放线菌素D等阻止rRNA聚合酶作用的试剂处理时，链会塌陷并浓缩成一个小的致密核仁，其中有核糖核蛋白（RNP）和脱氧核糖核蛋白（DNP）的分离区域。NN的特性似乎与两栖类卵母细胞核仁项链的特性相似。环己酰亚胺或嘌呤霉素对一般蛋白质合成的抑制不会导致NN形成。我们认为，精氨酸饥饿期间NN的形成可能是某些快速周转的富含精氨酸的蛋白质异常耗尽的结果，这些蛋白质通常在核糖体RNA前体分子合成并加工成熟的过程中附着于其上。
