THE ALTERNATIVE SPLICING OF AN EXITRON DETERMINES THE SUBNUCLEAR LOCALIZATION OF THE ARABIDOPSIS DNA-GLYCOSYLASE MBD4L UNDER HEAT STRESS

CECCHINI NM; TORRES, JOSE R; LESCANO, IGNACIO; COBO, SANTIAGO; NOTA MF; MARIA ELENA ALVAREZ

Congreso; Congreso Conjunto SAIB-SAMIGE 2020; 2020

DNA glycosylase are critical enzymes that excise damaged bases from DNA leading to DNA repair and maintenance of genomic stability. The Arabidopsis MBD4-like (MBD4L) DNA glycosylase is a nuclear enzyme apparently involved in tolerance to genotoxic stresses. The MBD4L gene contains an exitron at its 5´ region. Exitrons are protein-coding cryptic introns within exons with a high potential to increase protein diversity through alternative splicing (AS). Here, we show that the MBD4L exitron retention or removal determines its nucleoplasmic or nucleolar localization in both Arabidopsis and Nicotiana benthamiana plants. Interestingly, heat-stress regulates the MBD4L AS and increase the abundance of the nucleolar exitron-spliced variant. Consistently, plants expressing a MBD4L version with a non-spliceable exitron show no nucleolar localization under this condition. Together, our findings indicate that the MBD4L exitron AS have a broad impact on enzyme location and possibly substrate access/specificity. This is a step forward in the understanding of exitrons and their associated functions.