Discontinuously synthesized mRNA from Trypanosoma brucei contains the highly methylated 5' cap structure, m7GpppA*A*C(2'-O)mU*A |
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Authors: | M S Freistadt G A Cross H D Robertson |
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Institution: | Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021. |
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Abstract: | 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 A*A*C(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. |
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