Phillips S C, Turner P C
Department of Biochemistry, University of Liverpool, UK.
Gene. 1992 Jul 15;116(2):181-6. doi: 10.1016/0378-1119(92)90514-p.
Expression of the U7 gene, encoding mouse U7 snRNA, following microinjection into Xenopus oocytes is both accurate and efficient, giving rise to mature U7 snRNA and a precursor with an 8-nucleotide (nt) 3' extension. The mouse U7 gene promoter, which is similar to that of the vertebrate major U genes comprising a DSE, a PSE and a 3' box, with the same spatial arrangement, is as efficient as the Xenopus U2 gene promoter in this assay. A deletion analysis of the mouse U7 gene identified sequences downstream from the 3' box, within the region (nt +74 to +196), which seem to have a negative regulatory effect upon the frequency of transcription initiation and are also required for accurate 3' end formation. Sequences in the nt -1699 to -431 region also seemed to have a negative effect on the level of transcription. In addition, sequences upstream from the PSE, within the nt -65 to -421 region, are necessary for accurate and efficient synthesis of mature U7 snRNA. Finally, the mouse U7 snRNA may not form a functional snRNP in Xenopus oocytes due to defective snRNP assembly and/or nuclear import.
编码小鼠U7 snRNA的U7基因在显微注射到非洲爪蟾卵母细胞后，其表达既准确又高效，可产生成熟的U7 snRNA和一个具有8个核苷酸（nt）3'延伸的前体。小鼠U7基因启动子与脊椎动物主要U基因的启动子相似，包含一个DSE、一个PSE和一个3'框，具有相同的空间排列，在该实验中与非洲爪蟾U2基因启动子效率相当。对小鼠U7基因的缺失分析确定了3'框下游、区域（nt +74至+196）内的序列，这些序列似乎对转录起始频率有负调控作用，并且对于准确的3'末端形成也是必需的。nt -1699至-431区域的序列似乎也对转录水平有负面影响。此外，PSE上游、nt -65至-421区域内的序列对于成熟U7 snRNA的准确高效合成是必需的。最后，由于snRNP组装和/或核输入存在缺陷，小鼠U7 snRNA可能无法在非洲爪蟾卵母细胞中形成功能性snRNP。
