Wormington W M
Department of Biochemistry, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254.
Dev Biol (N Y 1985). 1988;5:227-40. doi: 10.1007/978-1-4615-6817-9_8.
The Xenopus ribosomal protein genes provide an excellent system to elucidate the complex regulation encompassing 60 functionally related proteins present in equimolar amounts in ribosomal subunits. Oogenesis and embryogenesis provide unique opportunities to investigate ribosome biosynthesis in situations wherein gene activation of individual components is uncoupled from assembly of the ribosomal subunits. This chapter has focused on the basic parameters that control ribosomal protein gene expression during development. Translational control is clearly a major level for coordinating the regulation of these genes during development, as is posttranslational stability of the ribosomal proteins and RNA splicing of the L1 gene. In addition to these levels of control under active investigation, a number of intriguing problems remain to be addressed in any detail. For example, the mechanisms that balance ribosomal protein production with subunit assembly in oocytes remain to be determined. Resolution of these events must also define the processes by which ribosomal proteins, upon synthesis in the cytoplasm, are first translocated to the nucleus and subsequently to the nucleolus for subunit assembly. Functional approaches in which these genes are assayed for accurate developmental control in microinjected oocytes and fertilized eggs will undoubtedly provide information on the synthesis of this eukaryotic organelle and the signals responsible for altering these processes at different developmental stages.
非洲爪蟾核糖体蛋白基因提供了一个极佳的系统，用以阐明围绕核糖体亚基中以等摩尔量存在的60种功能相关蛋白的复杂调控。卵子发生和胚胎发生为研究核糖体生物合成提供了独特的机会，在这些情况下，单个组分的基因激活与核糖体亚基的组装是解偶联的。本章重点关注了在发育过程中控制核糖体蛋白基因表达的基本参数。翻译控制显然是在发育过程中协调这些基因调控的一个主要层面，核糖体蛋白的翻译后稳定性和L1基因的RNA剪接也是如此。除了这些正在积极研究的控制层面外，还有许多有趣的问题有待详细探讨。例如，卵母细胞中核糖体蛋白产生与亚基组装之间平衡的机制仍有待确定。解决这些问题还必须明确核糖体蛋白在细胞质中合成后首先转运到细胞核，随后再转运到核仁进行亚基组装的过程。对这些基因在显微注射的卵母细胞和受精卵中进行精确发育控制检测的功能方法，无疑将提供有关这种真核细胞器合成以及在不同发育阶段改变这些过程的信号的信息。
