7SK snRNA methylphosphate capping enzyme (MEPCE)

The 7SK snRNA methylphosphate capping enzyme (MEPCE) is an RNA methyltransferase that catalyzes the methylation of the 5′ γ-phosphate of the human 7SK small nuclear RNA (snRNA), forming a unique monomethyl phosphate cap structure[1][3]. This cap modification is essential for RNA stability and proper function within the 7SK small nuclear ribonucleoprotein (snRNP) complex, a key regulator of RNA polymerase II transcription elongation[3][2]. MEPCE functions as both an enzyme and a structural component in the 7SK snRNP; its non-enzymatic role involves promoting the interaction between the RNA-binding protein LARP7 and 7SK snRNA, thereby further stabilizing the RNA and supporting the assembly of the snRNP complex[1][2][3][4]. By maintaining the integrity of the 7SK snRNP complex, MEPCE indirectly regulates the activity of positive transcription elongation factor b (P-TEFb) and thus plays a critical role in the control of gene expression[1][2][3]. No approved drugs selectively target MEPCE as of 2025, and there are no established clinical biomarkers or safety concerns related to direct inhibition. Key biological insights: - Major source of 7SK capping activity in human cells, required for 7SK RNA stability[1][3]. - Serves critical capping-independent functions: stabilizes RNA–protein interactions and promotes assembly of the 7SK snRNP complex[1][2][4]. - Loss or dysfunction could impact broad cellular transcriptional control via improper regulation of P-TEFb[2][3]. - Classified as an enzyme (RNA methyltransferase) with unique product retention characteristics, remaining strongly bound to its capped RNA product after catalysis[3][5]. No direct disease-modifying therapies exist for MEPCE as a target. However, aberrant function or regulation may be implicated in disorders of transcription or cell growth, including certain cancers[3][4].

Other names

BCDIN3MePCEBin3 homologFLJ20257Bicoid-interacting protein 3 homologbin3bicoid-interacting 3 homolog

Not applicable (no known modulatory drugs), but mechanistically: methylates 5′ γ-phosphate of 7SK snRNA; stabilizes RNA-protein complexes and regulates transcription by modulating 7SK snRNP