Preparation of N-2,N-2,7-trimethylguanosine affinity columns

2,2,7-trimethylguanosine (TMG) binding proteins from human cells were purif ied through TMG-affinity columns. TMG synthesis was improved and the TMG ob tained was shown to be similar to the TMG in the 5' cap of the UsnRNAs. The eluates obtained with TMG-affinity chromatographies were very different fr om those isolated with m(7)G-affinity columns, thus suggesting that specifi c TMG-binding proteins were obtained. The fraction may be enriched with fac tors associated with import and/or hypermethylation of UsnRNPs.