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首页> 外文期刊>Molecular and Cellular Biology >The phylogenetically invariant ACAGAGA and AGC sequences of U6 small nuclear RNA are more tolerant of mutation in human cells than in Saccharomyces cerevisiae.
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The phylogenetically invariant ACAGAGA and AGC sequences of U6 small nuclear RNA are more tolerant of mutation in human cells than in Saccharomyces cerevisiae.

机译：U6小核RNA的系统发生不变的ACAGAGA和AGC序列比酿酒酵母更能耐受人类细胞中的突变。

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U6 small nuclear RNA (snRNA) is the most highly conserved of the five spliceosomal snRNAs that participate in nuclear mRNA splicing. The proposal that U6 snRNA plays a key catalytic role in splicing [D. Brow and C. Guthrie, Nature (London) 337:14-15, 1989] is supported by the phylogenetic conservation of U6, the sensitivity of U6 to mutation, cross-linking of U6 to the vicinity of the 5' splice site, and genetic evidence for extensive base pairing between U2 and U6 snRNAs. We chose to mutate the phylogenetically invariant 41-ACAGAGA-47 and 53-AGC-55 sequences of human U6 because certain point mutations within the homologous regions of Saccharomyces cerevisiae U6 selectively block the first or second step of mRNA splicing. We found that both sequences are more tolerant to mutation in human cells (assayed by transient expression in vivo) than in S. cerevisiae (assayed by effects on growth or in vitro splicing). These differences may reflect different rate-limiting steps in the particular assays used or differential reliance on redundant RNA-RNA or RNA-protein interactions. The ability of mutations in U6 nucleotides A-45 and A-53 to selectively block step 2 of splicing in S. cerevisiae had previously been construed as evidence that these residues might participate directly in the second chemical step of splicing; an indirect, structural role seems more likely because the equivalent mutations have no obvious phenotype in the human transient expression assay.
机译：U6小核RNA（snRNA）是参与核mRNA剪接的五个剪接snRNA中保守性最高的。 U6 snRNA在剪接中起关键催化作用的提议[D. Brow and C. Guthrie，Nature（London）337：14-15，1989]受到以下方面的支持：U6的系统发育保守性，U6对突变的敏感性，U6与5'剪接位点附近的交联以及U2和U6 snRNA之间广泛碱基配对的遗传证据。我们选择突变人U6的系统发育不变的41-ACAGAGA-47和53-AGC-55序列，因为酿酒酵母U6同源区内的某些点突变选择性地阻断了mRNA剪接的第一步或第二步。我们发现，与酿酒酵母（通过对生长或体外剪接的影响进行分析）相比，这两个序列对人细胞中的突变（通过体内瞬时表达进行分析）都更耐受突变。这些差异可能反映了所用特定测定法中不同的限速步骤，或对冗余RNA-RNA或RNA-蛋白质相互作用的不同依赖。先前已将U6核苷酸A-45和A-53的突变选择性阻断酿酒酵母中的第2步剪接的能力作为这些残基可能直接参与剪接的第二化学步骤的证据。间接的结构作用似乎更有可能，因为在人类瞬时表达分析中，等效突变没有明显的表型。

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