Immunospecific retention of oligonucleotides possessing N⁶ methyladenosine and 7 methylguanosine

Antibodies specific for N⁶ methyladenosine (m⁶A) and for 7-methylguanosine (m⁷G) were immobilized on Sepharose and the resulting immunoadsorbents tested for their ability to retain specific oligonucleotides possessing the corresponding antigenic haptens (i.e. m⁶A and m⁷G). Results obtained with oligonucleotides derived from ribonuclease T₁ digests of Escherichia coli tRNA (previously labeled with [methyl ³H]methionine) indicated that each immunoadsorbent quantitatively and exclusively retained those methyl-³H-labelled oligonucleotides possessing [methyl-³H]m⁶A and [methyl-³#]m⁷G. Elution and subsequent characterization of [methyl-³H]m⁷G. retained methyl-³H labeled oligonucleotides via DEAE-cellulose chromatography revealed the presence of several small oligonucleotides containing m⁷G and a single, larger oligonucleotide containing m⁶A. These findings are in accord with previously sequenced structures which indicate that numerous bacterial tRNA species possess m⁷G while only tRNA(Val) contains m⁶A.