Discontinuously synthesized mRNA from Trypanosoma brucei contains the highly methylated 5' cap structure, m7GpppA*A*C(2'-O)mU*A.
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.
Freistadt
M S
MS
Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021.
Cross
G A
GA
Robertson
H D
HD
D000818:Animals; D008745:Methylation; D009708:Nucleotidases; D010727:Phosphoric Diester Hydrolases; D012314:RNA Cap Analogs / Q000302:isolation & purification*; D012315:RNA Caps / Q000302:isolation & purification*; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000302:isolation & purification; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014346:Trypanosoma brucei brucei / Q000235:genetics*
D012314:RNA Cap Analogs; D012315:RNA Caps; D012333:RNA, Messenger; D009708:Nucleotidases; D015719:Single-Strand Specific DNA and RNA Endonucleases; D010727:Phosphoric Diester Hydrolases