Subnuclear localization of the MBD4L DNA glycosylase splicing isoforms

CECCHINI NM; TORRES JR; NOTA F; COBO S; ALVAREZ ME

Capital Federal, Buenos Aires

Congreso; LIII Reunión Anual SAIB; 2017

SAIB

DNA glycosylases are key enzymes for organisms? genome stability mediating DNA damage repair. Among them, MBD4L is a nuclear Arabidopsis DNA glycosylase acting during stress conditions. Interestingly, MBD4L gene can generate two-isoforms through the retention of a protein-coding cryptic intron (exitron). It is believed that exitron splicing events result in protein versions with alternative functional domains and/or post-translational modifications. Taking this into account, we analyzed MBD4L splicing-isoforms transcript levels, subcelular localization and contribution to damaged DNA correction. We found that the MBD4L alternative transcripts changed their relative levels depending on the stress applied. Surprisingly, when expressed as GFP fusions each of the MBD4 isoforms located at different subnuclear compartments in both Arabidopsis and Nicotiana benthamiana plants. Moreover, some stresses induced dynamic changes in enzyme subnuclear localization. On the other hand, although showing distinctive localization the overexpression of both MBD4L isoforms increased resistance to a DNA damaging agent. Altogether, our results indicate that MBD4L location can be driven by exitron alternative splicing mechanisms. However, additional levels of control may determine differential subcellular requirements for MBD4L isoforms under particular circumstances. A putative model for MBD4L nuclear role/localization will be presented.