Differences in Activity of N2 -Guanine tRNA Methyltransferase II Among Several Inbred Strains of Mice2

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Abstract
The tRNA methyltransferase activities of C57BL/6J, C57L/J, C58/J, AKR/J, and C3H/HeJ inbred mice were studied with the use of various amino acid-specific Escherichia coli tRNA's as substrates. Mice from two strains with high incidence of spontaneous leukemia (AKR/J and C58/J) exhibited levels of liver N2-guanine tRNA methyltransferase II (N2-MeGII) activity that were double those of two strains of mice with low incidence of spontaneous leukemia (C57BL/6J and C57L/J). Activities of liver and kidney N2-MeGII of the high spontaneous hepatoma strain C3H/HeJ were also found to be twice as high as those of C57BL/6J mice. The activities of other tRNA base-specific liver tRNA methyl-transferases were very similar in all strains studied. The N2-MeGII activity of the F1 progeny of a cross between C57BL/6J and C3H/HeJ showed levels of activity intermediate to those of the parental strains. Activities of liver N2-MeGII of two inbred strains of mice that differ in their H-2 haplotype (C57BL/10SnJ and the congenic strain B10.BR/SgSnJ) were also compared. Both C57BL/ 10SnJ and B10.BR/SgSnJ strains exhibited low levels of liver N2-MeGII activity, indicating that H-2 does not directly control the activity of this enzyme.