Open AccessThe 2′-O-Ribose Methyltransferase for Cap 1 of Spliced Leader RNA and U1 Small Nuclear RNA in Trypanosoma brucei
Author(s) -
Jesse R. Zamudio,
Bidyottam Mittra,
Silvie Foldynová-Trantírková,
Gusti M. Zeiner,
Julius Lukeš,
Janusz M. Bujnicki,
Nancy R. Sturm,
David A. Campbell
Publication year - 2007
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.00647-07
Subject(s) - biology , trypanosoma brucei , five prime cap , rna , rna splicing , methylation , microbiology and biotechnology , small nuclear rna , ribose , messenger rna , rna methylation , guide rna , methyltransferase , biochemistry , rna editing , rna dependent rna polymerase , dna , enzyme , gene , crispr , cas9
mRNA cap 1 2′-O -ribose methylation is a widespread modification that is implicated in processing, trafficking, and translational control in eukaryotic systems. The eukaryotic enzyme has yet to be identified. In kinetoplastid flagellatestrans -splicing of spliced leader (SL) to polycistronic precursors conveys a hypermethylated cap 4, including a cap 0 m7 G and seven additional methylations on the first 4 nucleotides, to all nuclear mRNAs. We report the first eukaryotic cap 1 2′-O -ribose methyltransferase, TbMTr1, a member of a conserved family of viral and eukaryotic enzymes. Recombinant TbMTr1 methylates the ribose of the first nucleotide of an m7 G-capped substrate. Knockdowns and null mutants of TbMTr1 inTrypanosoma brucei grow normally, with loss of 2′-O -ribose methylation at cap 1 on substrate SL RNA and U1 small nuclear RNA. TbMTr1-null cells have an accumulation of cap 0 substrate without further methylation, while spliced mRNA is modified efficiently at position 4 in the absence of 2′-O -ribose methylation at position 1; downstream cap 4 methylations are independent of cap 1. Based on TbMTr1-green fluorescent protein localization, 2′-O -ribose methylation at position 1 occurs in the nucleus. Accumulation of 3′-extended SL RNA substrate indicates a delay in processing and suggests a synergistic role for cap 1 in maturation.