JBC, Vol. 252, Issue 17, 5981-5985, Sep, 1977
In vitro studies on the methylation of histones in rat brain nuclei
J. A. Duerre, J. C. Wallwork, D. P. Quick and K. M. Ford
When isolated nuclei from 12-day-old rat brains were incubated with
S-adenosyl-L-[methyl-3H]methionine, significant amounts of 3H-methyl were
incorporated into lysyl residues in histones H3 and H4. About 0.024% of the
total methylation sites on histone H3 and 0.013% of the sites on histone H4
were unmethylated at the time the nuclei were isolated. Methylation of
these sites proceeded stepwise, progressing to a stable ratio of
0.93:1.0:0.17 for N epsilon-mono-, N epsilon-di-, and N
epsilon-trimethyllysine in histone H3 and 0.19:1.0 for N epsilon-mono- and
N epsilon-dimethyllysine in histone H4. The Km values of the enzyme for
S-adenosyl-L-methionine were 11.5 +/- 1.1 micron and 12.5 +/- 1.3 micron
with histones H3 and H4 as methyl acceptors, respectively. The Vmax values
were 11.1 and 5.3 pmol of 3H-methyl incorporated/min/mg of histone H3 and
H4, respectively. Since histone H3 contains 2 mol of N
epsilon-methyllysine/mol and histone H4 contains 1 mol/mol, no difference
in the overall rates of methylation can be deduced from the data.
S-Adenosyl-L-homocysteine, one of the products of the reaction, was a
competitive inhibitor with respect to S-adenosyl-L-methionine. The Ki
values for S-adenosyl-L-homocysteine were 5.5 +/- 0.4 micron and 5.9 +/-
0.5 micron with histones H3 and H4 as methyl acceptors, respectively.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
