  A quantum mechanical model on histone modification is proposed. Along with
the methyl / acetate or other groups bound to the modified residues the torsion
angles of the nearby histone chain are supposed to participate in the quantum
transition cooperatively. The transition rate W is calculated based on the
non-radiative quantum transition theory in adiabatic approximation. By using
W's the reaction equations can be written for histone modification and the
histone modification level can be calculable from the equations, which is
decided by not only the atomic group bound to the modified residue, but also
the nearby histone chain. The theory can explain the mechanism for the
correlation between a pair of chromatin markers observed in histone
modification. The temperature dependence and the coherence-length dependence of
histone modification are deduced. Several points for checking the proposed
theory and the quantum nature of histone modification are suggested as follows:
1, The relationship between lnW and 1/T is same as usual protein folding. The
non-Arhenius temperature dependence of the histone modification level is
predicted. 2, The variation of histone modification level through point
mutation of some residues on the chain is predicted since the mutation may
change the coherence-length of the system. 3, Multi-site modification obeys the
quantum superposition law and the comparison between multi-site transition and
single modification transition gives an additional clue to the testing of the
quantum nature of histone modification.
