J. Biol. Chem., Vol. 255, Issue 5, 2062-2066, 03, 1980
Initiator RNA synthesis upon ribonucleotide depletion. Evidence for base substitutions
BY Tseng and M Goulian
Nearest neighbor frequencies in initiator RNA (iRNA) of a human lymphocyte
cell line have been measured in isolated nuclei under conditions where
ribonucleotides have been omitted from the incubation. Deoxynucleotides are
incorporated in iRNA to a limited extent for the omitted cognate
ribonucleotide. In addition, upon omission of a ribonucleotide, changes in
the nearest neighbor frequencies also occur indicating base substitution of
another ribonucleotide. The base substitutions that have been observed are
the incorporation of rA for rG or rU. Substitution for rA has not been
observed. When rC is omitted, a change in all nearest neighbor frequencies
occurs, suggesting possibly an unusual role for rC. The substitutions
demonstrate the unique features of iRNA synthesis and point out possible
alterations in iRNA that may occur in vivo when nucleotide pools are
altered.