Freistadt M S, Cross G A, Robertson H D
Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021.
J Biol Chem. 1988 Oct 15;263(29):15071-5.
Trypanosoma brucei mRNA is discontinuously synthesized via the 5' addition of a "mini-exon" sequence. The mini-exon-specific cap structure was purified from a complete RNase T2 and phosphatase digest of in vivo 32P-labeled poly(A)+RNA. The purified cap structure was sequenced by a series of partial and complete enzymatic digests by nuclease P1 and venom phosphodiesterase. This approach demonstrated that the T. brucei mini-exon cap structure consists of N7-methylguanosine linked in a conventional 5'-5' triphosphate bond to five nucleotides, in the sequence AAC(2'-O)mU*A (asterisks denote modifications that were not fully characterized in this work). 2'-O-methylations and other modifications appear to be present in this novel cap structure, which could have a functional role in the metabolism of the mini-exon.
布氏锥虫信使核糖核酸（mRNA）是通过“微型外显子”序列的5'端添加而间断合成的。微型外显子特异性帽状结构是从体内32P标记的聚腺苷酸（poly(A)+）RNA的完整核糖核酸酶T2和磷酸酶消化物中纯化得到的。通过核酸酶P1和蛇毒磷酸二酯酶进行的一系列部分和完全酶促消化对纯化的帽状结构进行了测序。该方法表明，布氏锥虫微型外显子帽状结构由通过常规 的5'-5'三磷酸键与五个核苷酸相连的N7-甲基鸟苷组成，其序列为AAC(2'-O)mU*A（星号表示在本研究中未完全表征的修饰）。2'-O-甲基化和其他修饰似乎存在于这种新型帽状结构中，这可能在微型外显子的代谢中发挥功能作用。
