Project description:We report our newly developed method for high-throughput sequencing of 2'-O methylation sites using positive signal and site specific approach. The pilot experiment using MiSeq generated ~2.5 million reads per sample. The 2'-O methylation site identification produced a promising distribution pattern matching known sites. For accurate and sensitive base call, >10 million reads are required per sample as evidenced in the NextSeq experiment.
Project description:Human genome encodes nine protein arginine methyltransferases (PRMT1–9), which catalyze three types of arginine methylation: monomethylation (MMA), asymmetric dimethylation (ADMA), and symmetric dimethylation (SDMA). These modifications can alter protein-protein and protein-nucleic acid interactions and play critical roles in transcription regulation and RNA metabolism. A few years ago, we characterized the newest member of the PRMT family–PRMT9 as a SDMA modifying enzyme and identified the splicing factor SF3B2 as its methylation substrate, linking its function to pre-mRNA splicing. However, the biological function of PRMT9 and the molecular mechanism by which PRMT9-catalyzed SF3B2 arginine methylation regulates pre-mRNA splicing remain largely unknown. Here, by charactering an intellectual disability patient-derived PRMT9 mutation (G189R) and establishing a Prmt9 conditional knockout (cKO) mouse model, we uncovered an important function of PRMT9 in neuronal development. We found that G189R mutation completely abolishes PRMT9 methyltransferase activity and destabilizes the protein by promoting its ubiquitination and proteasome degradation. PRMT9 loss in hippocampal neurons alters RNA splicing of ~1800 transcripts, which likely account for the abnormal synapse development and impaired learning and memory observed in the Prmt9 cKO mouse. Mechanistically, we discovered a critical protein-RNA interaction between the arginine 508 (R508) of SF3B2, the site that is exclusively methylated by PRMT9, and the pre-mRNA anchoring site, a cis-regulatory element located upstream of the branch point sequence (BPS). Additionally, we provide strong evidence that supports SF3B2 being the major and likely only substrate of PRMT9, thus highlighting the conserved function of PRMT9/SF3B2 axis in pre-mRNA splicing regulation.
Project description:The glycolytic enzyme, pyruvate kinase Pyk1 maintains telomere heterochromatin by phosphorylating histone H3T11 (H3pT11), which promotes SIR (silent information regulator) complex binding at telomeres and prevents autophagy-mediated Sir2 degradation. However, the exact action mechanism of H3pT11 is poorly understood. Here, we identify Dot1-catalyzed H3K79 tri-methylation (H3K79me3) as the downstream effector of H3pT11 and uncover how this histone crosstalk regulates autophagy and telomere silencing. Mechanistically, Pyk1-catalyzed H3pT11 directly reduces the binding of Dot1 to chromatin and inhibits Dot1-catalyzed H3K79me3, which leads to transcriptional repression of autophagy genes and reduced autophagy. Despite the antagonism between H3pT11 and H3K79me3, they synergically promote the binding of SIR complex at telomeres to maintain telomere silencing. Furthermore, we identify Reb1 as a telomere-associated factor that recruits Pyk1-containing SESAME (Serine-responsive SAM-containing Metabolic Enzyme) complex to telomere regions to phosphorylate H3T11 and prevent the invasion of H3K79me3 from euchromatin into heterochromatin to maintain telomere silencing. Together, these results uncover a novel histone crosstalk and provide insights into dynamic regulation of silent heterochromatin and autophagy in response to cell metabolism.
Project description:ASH-1 orthologs are H3K36-specific methyltransferases that are conserved from fungi to humans but are poorly understood, in part because they are typically essential for viability. Here we examine the H3K36 methylation pathway of Neurospora crassa, which we find has just two H3K36 methyltransferases, ASH-1 and RNA polymerase II-associated SET-2. Our investigation of the interplay between SET-2 and ASH-1 uncovered a regulatory mechanism connecting ASH-1-catalyzed H3K36 methylation to repression of poorly transcribed genes. Our findings provide new insight into ASH-1 function, H3K27me2/3 establishment, and repression at facultative heterochromatin.