The structure of ribosomal protein genes and the control mechanisms of their expression

真核核糖体的生物发生需要四个RNA和70多个不同的核糖体蛋白质分子的等摩尔积累。通过协调调节，这种化学计量比在广泛的生理条件下保持不变。本研究旨在研究单个核糖体蛋白基因的结构，以探讨其调控机制。通过杂交选择翻译，从S 8-9 S多聚(A)-核糖核酸的再生大鼠肝脏文库中分离到与核糖体蛋白编码基因S11、S17、S26、L5、L7a、L27、L30、L31、L35a和L37a互补的克隆。测定了这些基因的核苷酸序列。根据核苷酸序列推测这些蛋白质的结构，以证实这些克隆的同源性。利用重组DNA，我们发现这些蛋白质的相对丰度在肝部分切除后增加。它们的最高水平约为正常大鼠肝脏的两倍，并在术后12-18h达到最高水平。大鼠核糖体蛋白基因是由15-20个成员组成的多基因家族，以cDNA为探针进行Southern印迹分析。我们从大鼠基因组文库中分离到S11、L27和L35a的多个独立克隆。对抗性位点的分析表明，它们都缺乏介导性序列。这些基因与cDNA杂交分子的热稳定性表明，这些基因的核苷酸序列与cDNA序列有不同程度的相似性。这些基因缺乏中间序列，它们包含富含(A)的区域，并且它们的两侧有直接重复。因此，核糖体蛋白基因家族被证明主要由加工假基因组成。

The biogenesis of eucaryotic ribosomes requires an equimolar accumulation of four RNAs and over 70 different ribosomal protein molecules. This stoichiometry is maintained over a wide range of physiological conditions by coordinate regulation. We intended to study the structure of the genes for individual ribosomal proteins to investigate the control mechanisms.Clones containing cDNA inserts complementary to the mRNAs encoding ribosomal proteins S11, S17, S26, L5, L7a, L27, L30, L31, L35a, and L37a were isolated by hybrid-selected translation from the cDNA library made for 8-9 s poly(A)-RNA from regenerating rat liver. The nucleotide sequences of these cDNA were determined. The structures of these proteins were infered from the nucleotide sequences to confirm the identity of these clones.Using the recombinat DNAs, we found that the relative abundance of the mRNAs of these proteins increased after partial hepatectomy. Their maximal level was about twice that of normal rat liver, and was achieved 12-18 h after the operation. The abundance decreased near to the normal level after 48 h.The rat ribosomal protein genes comprise multigene families which contain 15-20 memberes as shown by the Southern blot anaylyses using the cDNAs as probes. We isolated many independent clones of S11,L27,and L35a from a rat genomic library. Analysis of the restiction sites showed that all of them lacked the intervening seguences. Thermal stability of the hybrid molecules beween these genes and the cDNAs indicated that the nucleotide sequences of these genes had various similarities to the the sequences of the cDNAs. These genes lacked the intervening sequence, they contained (A)-rich tracts, and they were flanked by direct repeats. Thus, the ribosomal protein gene families were proven to comprise mostly processed pseudogenes.