Roldán-Arjona, Teresa
Rodríguez Ariza, Rafael
Ponferrada-Marín, María Isabel
2013-08-30T09:38:04Z
2013-08-30T09:38:04Z
2009
http://hdl.handle.net/10396/10871
Arabidopsis ROS1 belongs to a family of plant
5-methycytosine DNA glycosylases that initiate
DNA demethylation through base excision. ROS1
displays the remarkable capacity to excise 5-meC,
and to a lesser extent T, while retaining the ability to
discriminate effectively against C and U. We found
that replacement of the C5-methyl group by halogen
substituents greatly decreased excision of the
target base. Furthermore, 5-meC was excised
more efficiently from mismatches, whereas excision
of T only occurred when mispaired with G.
These results suggest that ROS1 specificity arises
by a combination of selective recognition at the
active site and thermodynamic stability of the
target base. We also found that ROS1 is a low-turnover
catalyst because it binds tightly to the abasic
site left after 5-meC removal. This binding leads to a
highly distributive behaviour of the enzyme on DNA
substrates containing multiple 5-meC residues, and
may help to avoid generation of double-strand
breaks during processing of bimethylated CG
dinucleotides. We conclude that the biochemical
properties of ROS1 are consistent with its proposed
role in protecting the plant genome from excess
methylation.
application/pdf
eng
Oxford University Press
https://creativecommons.org/licenses/by-nc-nd/4.0/
Nucleic Acids Research 37 (13), 4264-4274 (2009)
Arabidopsis
DNA
ROS1 5-methylcytosine DNA glycosylase is a slow-turnover catalyst that initiates DNA demethylation in a distributive fashion
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