Editors' ChoiceBiochemistry

Dual action: Demethylase and ubiquitin ligase

Sci. Signal.  14 Apr 2015:
Vol. 8, Issue 372, pp. ec92
DOI: 10.1126/scisignal.aab3256

While testing for a role for the histone demethylase LSD2 in the DNA damage response, Yang et al. found that DNA damage promoted the polyubiquitylation and degradation of LSD2. In vitro ubiquitylation assays revealed that LSD2 itself possessed E3 ubiquitin ligase activity, exhibiting autoubiquitylation activity and activity toward O-GlcNAc transferase (OGT). OGT is known to interact with LSD2 and integrates nutritional status with posttranslational modification of proteins by transfer of β-N-acetylglucosamine to serine or threonine residues. Experiments with 293T cells transfected with tagged versions of ubiquitin, OGT, or LSD2 and with cells in which LSD2 was knocked down showed that OGT was ubiquitylated in an LSD2-dependent manner in cells. LSD2 mutants with either only demethylase activity (LSD2ER-AA) or only E3 ubiquitin ligase activity (LSD24CA) established that OGT ubiquitylation and degradation depended on the E3 ubiquitin ligase activity of LSD2. 293T cells in which LSD2 was knocked down exhibited clustered growth in culture, and introduction of wild-type or LSD24CA, but not LSD2ER-AA, inhibited colony formation in these cells, indicating that the E3 ubiquitin ligase activity was necessary to prevent this transformation-associated phenotype. Analysis of several different cancer cell lines showed that the abundance of LSD2 (protein and mRNA) was lower in the cancer cell lines than in 293T cells with the A549 lung cancer cell line having undetectable amounts of LSD2. Compared with control A549 cells, introduction of LSD2 with E3 ubiquitin ligase activity, but not LSD2ER-AA, resulted in smaller and fewer colonies and reduced the abundance of OGT. Overexpression of OGT in the A549 cells overexpressing LSD24CA resulted in growth and colony formation similar to that of the control cells, indicating that OGT was a relevant target of the E3 ubiquitin ligase activity of LSD2 in controlling growth. Thus, these data indicated that LSD2 is a bifunctional protein with two separable catalytic activities and that the E3 ubiquitin ligase activity toward OGT may suppress cancer growth.

Y. Yang, X. Yin, H. Yang, Y. Xu, Histone demethylase LSD2 acts as an E3 ubiquitin ligase and inhibits cancer cell growth through promoting proteasomal degradation of OGT. Mol. Cell 58, 47–59 (2015). [PubMed]