Deshmukh M, Tsay Y F, Paulovich A G, Woolford J L
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213-2683.
Mol Cell Biol. 1993 May;13(5):2835-45. doi: 10.1128/mcb.13.5.2835-2845.1993.
Ribosomal protein L1 from Saccharomyces cerevisiae binds 5S rRNA and can be released from intact 60S ribosomal subunits as an L1-5S ribonucleoprotein (RNP) particle. To understand the nature of the interaction between L1 and 5S rRNA and to assess the role of L1 in ribosome assembly and function, we cloned the RPL1 gene encoding L1. We have shown that RPL1 is an essential single-copy gene. A conditional null mutant in which the only copy of RPL1 is under control of the repressible GAL1 promoter was constructed. Depletion of L1 causes instability of newly synthesized 5S rRNA in vivo. Cells depleted of L1 no longer assemble 60S ribosomal subunits, indicating that L1 is required for assembly of stable 60S ribosomal subunits but not 40S ribosomal subunits. An L1-5S RNP particle not associated with ribosomal particles was detected by coimmunoprecipitation of L1 and 5S rRNA. This pool of L1-5S RNP remained stable even upon cessation of 60S ribosomal subunit assembly by depletion of another ribosomal protein, L16. Preliminary results suggest that transcription of RPL1 is not autogenously regulated by L1.
酿酒酵母的核糖体蛋白L1可结合5S rRNA，并能作为L1-5S核糖核蛋白（RNP）颗粒从完整的60S核糖体亚基中释放出来。为了解L1与5S rRNA之间相互作用的本质，并评估L1在核糖体组装和功能中的作用，我们克隆了编码L1的RPL1基因。我们已证明RPL1是一个必需的单拷贝基因。构建了一个条件性无效突变体，其中RPL1的唯一拷贝受可抑制的GAL1启动子控制。L1的缺失会导致体内新合成的5S rRNA不稳定。L1缺失的细胞不再组装60S核糖体亚基，这表明L1是稳定60S核糖体亚基组装所必需的，但不是40S核糖体亚基组装所必需的。通过L1和5S rRNA的共免疫沉淀检测到了一种不与核糖体颗粒相关的L1-5S RNP颗粒。即使通过缺失另一种核糖体蛋白L16来停止60S核糖体亚基的组装，这一L1-5S RNP库仍保持稳定。初步结果表明，RPL1的转录不受L1的自身调节。
