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种rna和超过70种不同的核糖体蛋白分子的等摩尔积累。这种化学计量通过坐标调节在广泛的生理条件下维持。我们打算研究单个核糖体蛋白的基因结构，以探讨其控制机制。从再生大鼠肝脏8-9 s poly(A)-RNA cDNA文库中，通过杂交选择翻译分离到与编码核糖体蛋白S11、S17、S26、L5、L7a、L27、L30、L31、L35a和L37a mrna互补的cDNA插入克隆。测定这些cDNA的核苷酸序列。从核苷酸序列推断出这些蛋白质的结构，以确认这些克隆的身份。使用重组dna，我们发现这些蛋白的mrna的相对丰度在部分肝切除术后增加。在术后12 ~ 18 h达到最大水平，约为正常大鼠肝脏的2倍。48 h后丰度下降到接近正常水平。用dna作为探针进行Southern blot分析表明，大鼠核糖体蛋白基因是一个多基因家族，包含15-20个成员。我们从一个大鼠基因组文库中分离出许多独立的S11、L27和L35a克隆。限制性位点分析表明，它们都缺乏干预序列。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的序列有各种相似之处。这些基因缺乏干预序列，它们含有(A)-富束，它们的两侧有直接重复序列。因此，核糖体蛋白基因家族被证明主要由加工过的假基因组成。

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.