METHYL ACTIVATION AND sRNA METHYLATION BY SOLUBLE FRACTIONS OF SEVERAL VERTEBRATE LIVERS

Abstract

The amount of liver ATP: L-methionine S-adenosyltransferase activity varies widely in vertebrates from trace amounts in certain lower vertebrates, e.g. shark or turtle, to relatively large quantities in mammals, e.g. mouse or rabbit. The liver from male mice of a particular stock had only two-thirds the activity of female mouse liver. This difference is not explained by the difference between the sexes in number of X-chromosomes, since female mice with only one X-chromosome (X/0) had the same levels of liver S-adenosyltransferase activity as normal females with two X-chromosomes.sRNA methylase activity from mouse, shark, and rabbit liver supernatant fractions were studied with mouse, shark, and Escherichia coli sRNA. Highspeed supernatant fractions from both rabbit embryonic liver and mouse hepatoma hypermethylated E. coli sRNA which had been previously methylated by adult rabbit or mouse liver supernatant fractions. Hepatoma methylase(s) acts in an analogous manner to that of a species-specific interaction with heterologous and homologous sRNA.A calculation is made comparing the amount of sRNA methylase activity detected in vitro with mouse liver sRNA, with one which is theoretically derived; similar values are obtained. The variation found in vertebrate liver with respect to methyl activation and sRNA methylation is discussed.