SUBNUCLEARLOCALIZATION OF THE MBD4L DNA GLYCOSYLASE SPLICING

ISOFORMS

Cecchini N, Torres J, Nota F,Lescano I, Cobo S, Álvarez M E

Centro de investigaciones enQuímica Biológica de Córdoba (CIQUIBIC, CONICET-UNC), Facultad de CienciasQuímicas, Universidad Nacional de Córdoba.

nikosestepario@gmail.com

DNA glycosylases are key enzymes fororganisms? genome stability mediating DNA damage repair. Among them, MBD4L is anuclear Arabidopsis DNA glycosylase acting during stress conditions.Interestingly, MBD4L gene can generate two isoformsthrough the retention of a protein coding cryptic intron (exitron). It isbelieved that exitron splicing events result in protein versions withalternative functional domains and/or post translational modifications. Takingthis into account, we analyzed MBD4L splicing isoforms transcript levels,subcelular localization and contribution to damaged DNA correction. We foundthat the MBD4L alternative transcripts changed their relative levels depending on thestress applied. Surprisingly, when expressed as GFP fusions each of the MBD4isoforms located at different subnuclear compartments in both

Arabidopsis and Nicotiana benthamiana plants. Moreover, some stressesinduced dynamic changes in enzyme subnuclear localization. On the other hand,although showing distinctive localization the overexpression of both MBD4Lisoforms increased resistance to a DNA damaging agent. Altogether, our resultsindicate that MBD4L location can be driven by exitron alternative splicingmechanisms. However, additional levels of control may determine differentialsubcellular requirements for MBD4L isoforms under particular circumstances. Aputative model for MBD4L nuclear role/localization will be presented.