The DNA glycosylase AtMBD4L mediates removal of 5-BrU from DNA in vivo

TORRES JR; LESCANO I; ALVAREZ ME

Congreso; RAFV Conference XXXIII Argentinian meeting of Plant Physiology; 2021

The base analog 5-bromouracil (5-BrU) can be incorporated into DNA by living cells during replication. 5-BrU is used in place of thymidine and is inserted opposite to adenine in DNA. However, 5-BrU can also be paired with guanine so if it is not removed, it can result in AT-GC transition mutations during subsequent replication cycles. DNA base modifications can be repaired by the excision repair system (BER). The DNA glycosylases are enzymes that participate in BER recognizing and removing the damaged DNA bases. Methyl-binding domain 4-like (MBD4L) is a monofunctional DNA glycosylase described in Arabidopsis that can efficiently remove uracil and uracil halogenated derivatives in vitro. For this reason, we asked if MBD4L is able to remove 5-BrU on DNA in vivo. To test this, we treated wild type (WT) and MBD4L mutant (mbd4l) plants with different concentrations (0, 100 y 200 uM) of 5-BrU, and analyzed its effects on plant development (root growth), DNA strand breaks (comet assays) and cell viability (propidium iodide staining). Our results suggest that MBD4L is essential to promote growth, DNA repair and cell viability of plants, counteracting the harmful effect of 5-BrU accumulation in DNA.