Nov 1, 1989

Gamma-monomethyl phosphate: a cap structure in spliceosomal U6 small nuclear RNA

Proceedings of the National Academy of Sciences of the United States of America
R Singh, R Reddy


U6 small nuclear RNA (snRNA), a component of eukaryotic spliceosomes, is required for splicing of nuclear pre-mRNAs. Whereas trimethylguanosine cap-containing U sn-RNAs are transcribed by RNA polymerase II, the U6 RNA is transcribed by RNA polymerase III and contains a nonnucleotide cap structure on its 5' end. We characterized the cap structure of human U6 snRNA and show that the gamma phosphate of the 5' guanosine triphosphate is methylated. The mobilities of in vivo-modified gamma phosphate from the 5' end of HeLa U6 RNA were identical to the synthetic monomethyl phosphate (CH3-O-P) in two-dimensional chromatography and two-dimensional electrophoresis. The cap structure of U6 RNA is distinct from all other cap structures characterized thus far.

Mentioned in this Paper

RNA Polymerase II
RNA Polymerase III
Small Nuclear RNA
Phosphate Measurement
RNA Caps
Nuclear mRNA Cis Splicing, via Spliceosome
U6 small nuclear RNA
RNA Splicing
Organopyrophosphorus Compounds

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