| 2009 |
MePCE caps 7SK snRNA in a LARP7-free state, likely co-transcriptionally. Upon incorporation into the 7SK snRNP, MePCE interacts with LARP7, which occludes MePCE's catalytic center and abolishes its capping activity. Despite loss of capping activity within the snRNP, MePCE retains a capping-independent function that promotes the LARP7–7SK interaction, stabilizing 7SK and facilitating assembly of a stable MePCE–LARP7–7SK subcomplex. |
Biochemical fractionation, co-immunoprecipitation, in vitro capping assays, RNAi knockdown with rescue experiments |
Nucleic acids research |
High |
19906723
|
| 2013 |
MePCE binds to the short 5'-terminal G1-U4/U106-G111 helix-tail motif of 7SK snRNA; both the overall RNA structure and specific nucleotides provide information for MePCE's specific binding. LARP7 binds the 3'-terminal hairpin and U-rich tail. These interactions direct assembly of the core 7SK/MePCE/LARP7 snRNP in vivo. |
In vivo RNA-protein interaction assays (immunoprecipitation of RNA–protein complexes with mutant 7SK constructs) |
Nucleic acids research |
Medium |
23471002
|
| 2018 |
X-ray crystal structures (2.0 Å and 2.1 Å) of the human MePCE methyltransferase domain bound to SAH and uncapped or capped 7SK substrates reveal that 7SK recognition is achieved via protein contacts to a 5'-hairpin–single-stranded RNA region, explaining MePCE specificity for 7SK and U6. The structures capture SAH and product RNA in near-transition-state geometry. Binding experiments show MePCE has higher affinity for capped versus uncapped 7SK, and kinetic data support slow product release, providing the mechanism for 7SK retention by MePCE after cap methylation. |
X-ray crystallography (2.0 Å / 2.1 Å), binding affinity measurements, kinetic assays |
Nature chemical biology |
High |
30559425
|
| 2018 |
MePCE binds to the histone H4 tail on chromatin and serves as a P-TEFb activator at specific genes controlling cellular identity. This histone-binding activity abolishes MePCE's RNA methyltransferase activity toward 7SK, explaining why chromatin-bound MePCE–P-TEFb complexes are not associated with the full 7SK snRNP and are competent to activate RNAP II. This crosstalk between histone-binding and RNA methylation activities regulates P-TEFb activation on chromatin in a 7SK- and Brd4-independent manner. |
ChIP, co-immunoprecipitation, in vitro histone-binding assays, RNA methyltransferase activity assays, RNAi knockdown with gene expression readouts |
Cell reports |
Medium |
29425494
|
| 2020 |
JMJD6 cleaves MePCE proteolytically in vivo and in vitro. Crystal structure of JMJD6 bound to methyl-arginine and enzymatic assays establish MePCE as a cognate substrate for JMJD6's proteolytic activity. Cleavage of MePCE disrupts the 7SK snRNP complex, releasing P-TEFb, and Jmjd6 knockout/overexpression modulates RNAP II CTD phosphorylation downstream. |
X-ray crystallography (JMJD6–methyl-arginine), in vitro and in vivo proteolytic assays, binding assays, Jmjd6 knockout and overexpression with CTD phosphorylation readout |
eLife |
High |
32048991
|
| 2019 |
A de novo MEPCE nonsense variant (p.Arg518*) causes nonsense-mediated mRNA decay, reducing MEPCE protein levels, which leads to secondary downregulation of LARP7 and 7SK snRNA, upregulation of HEXIM1, reduced HEXIM1–Cyclin-T1 binding, and hyperphosphorylation of the RNAP II CTD — indicating enhanced P-TEFb activation. Ectopic MEPCE expression rescued increased expression of P-TEFb-sensitive genes, establishing MEPCE's repressive role in P-TEFb-dependent transcription. |
Patient fibroblast analysis, mRNA/protein quantification, co-immunoprecipitation (HEXIM1–Cyclin-T1), RNAP II CTD phosphorylation assay, ectopic MEPCE rescue experiment, flavopiridol treatment |
Scientific reports |
Medium |
31467394
|
| 2023 |
In human cells, MePCE is required for stability of both U6 and 7SK snRNAs. A conserved 'Bin3-Box' domain present only in enzymes associated with 7SK regulation is important for Bin3/MePCE function with 7SK but not U6. An Amus–MePCE hybrid bearing the MePCE methyltransferase domain rescues U6 stability in Drosophila lacking Amus, demonstrating the conserved U6-capping function of the methyltransferase domain. |
Human cell MePCE depletion (snRNA stability assay), Drosophila genetic rescue with hybrid proteins, targeted mutagenesis of Bin3-Box |
Science advances |
Medium |
38100593
|
| 2024 |
In Drosophila, a catalytic-dead Bin3 mutant (Bin3Y795A) can still bind and stabilize 7SK snRNA and rescues all bin3 mutant phenotypes (reduced fecundity, neuromuscular defects), demonstrating that the methyltransferase catalytic activity of Bin3/MePCE is dispensable for 7SK snRNP stability and function in vivo. A metazoan-specific motif (MSM) outside the methyltransferase domain is required for a 7SK-independent, tissue-specific function of Bin3. |
Drosophila genetics (bin3 null mutants, catalytic point mutant Bin3Y795A, MSM deletion mutant Bin3ΔMSM), genetic epistasis with P-TEFb reduction, 7SK snRNA stability assay |
Genetics |
High |
37982586
|
| 2022 |
In fission yeast, the MePCE ortholog Bmc1 (Bin3/MePCE 1) functions together with Pof8 (LARP7 ortholog) and Thc1 in recognizing correctly folded telomerase RNA, promoting recruitment of the Lsm2-8 complex and assembly of functional telomerase holoenzyme; Bmc1 is required for wildtype telomerase activity and telomere length maintenance. |
Affinity purification of Pof8, telomerase activity assay, telomere length analysis, genetic knockouts |
Nature communications |
Medium |
35217638
|
| 2024 |
In human cells, LARP7 and MePCE are involved in early-stage telomerase RNA (hTR) biogenesis: their depletion inhibits conversion of the 3'-extended short (exS) precursor form into mature hTR and causes cytoplasmic accumulation of hTR, resulting in telomere shortening. |
Biochemical fractionation, RNA analysis of hTR processing intermediates, LARP7/MePCE depletion, telomere length measurement |
Nature communications |
Medium |
39009594
|
| 2025 |
Chromatin-associated MePCE interacts with R-loop processing and DNA repair factors and is recruited to DNA double-strand breaks (DSBs). MePCE depletion impairs DSB repair by homologous recombination, decreases RAD51 loading, and enhances R-loop levels at AsiSI-induced DSBs. MePCE depletion also increases LARP7 interaction with R-loops; LARP7 is degraded by BRCA1/BARD1 upon DSB, revealing dynamic regulation of the 7SK RNP at DSBs. |
Co-immunoprecipitation (MePCE with R-loop/repair factors), ChIP at AsiSI-induced DSBs, HR repair assay, RAD51 foci, R-loop immunofluorescence (S9.6), MePCE depletion |
Cell reports |
Medium |
40411785
|