Regulation of ribosomal protein gene expression in higher eukaryotes

(1)互补DNA克隆。我们分离了2个大鼠核糖体蛋白和4个鸡核糖体蛋白的CDNA克隆。这些dna不仅可以作为基因克隆的探针，还可以通过测序来了解核糖体的结构、功能和进化。(2)基因克隆。从鸡基因组文库中分离到4种核糖体蛋白基因L5、L7a、L30和L37a，并确定了这些基因的全核苷酸序列，分别扩增了8.5、4.5、4.0和3.5千碱基。(3)核糖体蛋白基因启动子区特征。这些基因既没有典型的CAAT盒，也没有典型的TATA盒。在转录起始位点周围有许多CpG二聚体，在启动子区域有几个GC盒，称为转录因子Spl的结合位点。这些发现在许多其他居家基因中也很常见。我们没有发现所有四个基因的启动子区域共有的特定核苷酸序列，似乎与转录调控有关。但是，对于两个或三个基因共有的转录调节因子和/或起始因子，有几个候选的结合子。在5S RNA结合蛋白L5基因的启动子区域也发现了与5S RNA基因内部转录控制区相似的序列。这些发现提示核糖体蛋白基因的表达受复杂的调控机制调控。这些候选调控元件的功能通过CAT试验和核提取物结合试验进行了分析。

(1)Complementary DNA cloning.We isolated CDNA clones for two rat ribososomal proteins and four chicken ribosomal proteins. The CDNAs were not only used as probes in gene cloning but also sequenced to provide information on the structure, function and evolution of the ribosomes.(2)Gene cloning.We isolated the clones of four kinds of ribosomal proteins genes, L5, L7a, L30, and L37a, from a chicken genomic library and determined the entire nucleotide sequences of the genes, expanding about 8.5, 4.5, 4.0, and 3.5 kilobases, respectively.(3)Features in the promoter region of the ribosomal protein genes.These genes do not have either canonical CAAT box or TATA box. There are many CpG dimers concentrated around the transcription initiation site and several GC boxes, known as the binding sites of the transcription factor Spl, in the promoter region. These findings are common to many other house keeping genes.We could not found specific nucleotide sequence that is common to promoter regions of all four genes and seems to be concerned in transcriptional regulation. But there are several candidates for the binding subs of the transcriptional regulation factors and/or initiation factors common to two or three genes. The sequence similar to the internal transcriptional control region of 5S RNA gene was also found in the promoter region of the gene of L5, the 5S RNA binding protein.These findings suggest that the expression of ribosomal protein gene is regulated by complicated control mechanisms. The function of these candidates of regulatory elements is being analyzed by CAT assay and the binding assay of nuclear extract.