Reparación por escisión de bases: función en el mantenimiento del genoma y el control epigenético

Dra. María Teresa Roldán. (Univ. Córdoba)

Jueves, 6 de junio de 2019. 12:00 h

Salón de Grados cicCartuja2

Base excision repair (BER) is a crucial defense pathway that replaces damaged DNA bases. It is a multistep process initiated by DNA glycosylases, small enzymes that excise the altered base and generate an intermediate that must be processed by additional proteins before repair is completed. BER has been extensively studied in bacteria, yeast, and mammals.

Results obtained so far in plants indicate that they share many BER components with other organisms, but possess some distinctive features. Among other BER innovations, plants have evolved an unique family of large DNA glycosylases that excise 5-methylcytosine (5-meC), allowing its replacement with unmethylated C. These enzymes, typified by Arabidopsis ROS1 and DME, initiate a BER-based, active DNA demethylation pathway that prevents hypermethylation and plays important functions in genome imprinting and seed development. After 5-meC excision, ROS1/DME proteins incise the sugar-phosphate backbone, generating single nucleotide gaps with non-canonical 3´-ends that are processed by additional BER enzymes, such as APE1L and ZDP. Another repair-related factor, DDB2, avoids accumulation of potentially harmful DNA demethylation intermediates and coordinates methylation and demethylation activities.

Thus, beyond its canonical role in genome maintenance, the plant DNA repair machinery performs critical functions in epigenetic regulation.

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