MLL methyltransferases regulate H3K4 methylation to ensure CENP-A assembly at human centromeres

Abstract

The active state of centromeres is epigenetically defined by the presence of CENP-A interspersed with histone H3 nucleosomes. While the importance of dimethylation of H3K4 for centromeric transcription has been highlighted in various studies, the identity of the enzyme(s) depositing these marks on the centromere is still unknown. The MLL (KMT2) family plays a crucial role in RNA polymerase II (Pol II)-mediated gene regulation by methylating H3K4. Here, we report that MLL methyltransferases regulate transcription of human centromeres. CRISPR-mediated down-regulation of MLL causes loss of H3K4me2, resulting in an altered epigenetic chromatin state of the centromeres. Intriguingly, our results reveal that loss of MLL, but not SETD1A, increases co-transcriptional R-loop formation, and Pol II accumulation at the centromeres. Finally, we report that the presence of MLL and SETD1A is crucial for kinetochore maintenance. Altogether, our data reveal a novel molecular framework where both the H3K4 methylation mark and the methyltransferases regulate stability and identity of the centromere.

Centromere inactivation during aging can be rescued in human cells

“…Centromeric transcription plays a crucial role in the incorporation of CENP-A and the stability of kinetochores 25,26 . Existing research indicates that specific histone modifications, particularly H3K4me2, are vital in regulating centromeric transcription 37,38 . To explore the potential epigenetic factors affecting centromeric transcription, we first examined the occupancy of heterochromatin mark at the centromeric DNA in aging cells.…”

“…Centromeric transcription plays a crucial role in the incorporation of CENP-A and the stability of kinetochores 25,26 . Existing research indicates that specific histone modifications, particularly H3K4me2, are vital in regulating centromeric transcription 37,38 .…”

To stay in shape and keep moving: MLL emerges as a new transcriptional regulator of Rho GTPases

“…Previous literature indicates that explosive filopodia formation occurs due to a number of reasons including depletion of ARP2/3 complex [ 10 ]. MLL has also been shown to affect the expression of a sizable number of proteins involved in regulation of actin cytoskeleton [ 11 , 12 ]. Thus, there is an overlap between MLL targets and Rho GTPase signalling pathway.…”

“…In addition, WDR5 has been shown to affect the plasticity of nucleus, which gives selective advantage to the cells migrating in 3D environments [ 28 ]. Moreover, MLL depletion causes downregulation of a considerable number of genes that play role in regulation of actin cytoskeleton [ 11 , 12 ]. MLL2 knockdown has also been shown to downregulate many genes that are essential for cell spreading, adhesion and maintaining polarity, resulting in spreading and migration defects [ 29 ].…”