Jesavel A Iguchi
University of Tsukuba, Japan
Title: RNA methylation stimulates mRNA recapping pathway in Trypanosoma brucei
Biography
Biography: Jesavel A Iguchi
Abstract
Trypanosoma brucei is a kinetoplastid protozoan parasite that causes African sleeping sickness in humans and Nagana in domestic animals. Virtually all kinetoplastid mRNA possess cap 4 structure (m7Gpppm6,2AmpAmpCmpm3Um) on the mature mRNA, which consists of standard cap 0 (m7Gppp-) with additional methylations at seven sites within the first four transcribed nucleosides. Trypanosoma brucei encodes a cytoplasmic recapping enzyme, TbCe1, which converts decapped monophosphorylated RNA into an unmethylated capped (GpppN-) RNA. However, in order to generate a translatable mRNA by TbCe1, the cap must be further methylated at (guanine N-7) position to form m7GpppN. We hypothesize that TbCmt1, which was previously shown to function as (guanine N-7) RNA methyltransferase, act together with TbCe1 in the cytoplasmic mRNA recapping pathway. We expressed the protein C-TEV-Protein A tag (PTP)-TbCmt1 fusion protein and showed that TbCmt1 is likely localized in the cytoplasm. We further demonstrated that TbCmt1 methyltransferase activity was stimulated by hypermethylation found in cap 4 structure. These results imply that TbCmt1 functions together with TbCe1 in the mRNA recapping pathway and suggests that mRNA recapping is selectively regulated by differential cap methylation. TbCmt1 may also act as a surveillance enzyme to ensure that only the hypermethylated capped RNAs return to the translational pool.