Histone Methyltransferase Dot1L Contributes to RIPK1 Kinase-Dependent Apoptosis in Cerebral Ischemia/Reperfusion.

Background Neuron apoptosis is a pivotal process for brain damage in cerebral ischemia. Dot1L (disruptor of telomeric silencing 1-like) is only known histone H3K79 methyltransferase. It is not clear whether the role and mechanism of Dot1L on cerebral ischemia is related to regulate neuron apoptosis. Methods and Results We use a combination of mice middle cerebral artery occlusion stroke and neurons exposed to oxygen-glucose deprivation followed by reoxygenation to investigate the role and mechanism of Dot1L on cerebral ischemia. We find knockdown or inhibition of Dot1L reversed ischemia-induced neuronal apoptosis and attenuated the neurons injury treated by oxygen-glucose deprivation followed by reoxygenation. Further, blockade of Dot1L prevents RIPK1 (receptor-interacting protein kinase 1)-dependent apoptosis through increased RIPK1 K63-ubiquitylation and decreased formation of RIPK1/Caspase 8 complexes. In line with this, H3K79me3 enrichment in the promoter region of deubiquitin-modifying enzyme A20 and deubiquitinase cylindromatosis gene promotes the increasing expression in oxygen-glucose deprivation followed by reoxygenation -induced neuronal cells, on the contrary, oxygen-glucose deprivation followed by reoxygenation decreases H3K79me3 level in the promoter region of ubiquitin-modifying enzyme cIAP1 (cellular inhibitors of apoptosis proteins), and both these factors ultimately cause K63-deubiquitination of RIPK1. Importantly, knockdown or inhibition of Dot1L in vivo attenuates apoptosis in middle cerebral artery occlusion mice and reduces the extent of middle cerebral artery occlusion -induced brain injury. Conclusions These data support for the first time, to our knowledge, that Dot1L regulating RIPK1 to the apoptotic death trigger contributes to cerebral ischemia injury. Therefore, targeting Dot1L serves as a new therapeutic strategy for ischemia stroke.