Reaction of HeLa cell methyl-labelled 28S ribosomal RNA with sodium bisulphite: a conformational probe for methylated sequences.

The reaction of 14C methyl-labelled HeLa cell 28 S ribosomal RNA with sodium bisulphite was studied. Using conditions under which 30% of the total cytidine residues were de-aminated to uridine, the reactivities of individual cytidine residues near particular methylation sites differed widely; some underwent almost quantitative reaction, some showed intermediate reactivity and others were almost inert. The possible value of this method as a conformational probe for ribosomal RNA is discussed.