DGCR8 promotes nascent transcription independently of DROSHA.

DiGeorge syndrome critical region gene 8 (DGCR8) is best known as the RNA-binding subunit of the microprocessor complex required for canonical microRNA (miRNA) biogenesis. Whether DGCR8 also exerts a direct, microprocessor-independent function in the RNA polymerase II (Pol II) transcription cycle remains unclear. Here, we combined rapid protein degradation with nascent transcription profiling to examine the immediate role of DGCR8 in transcriptional regulation in mouse embryonic stem cells (mESCs). We found that DGCR8 broadly occupies promoters and transcription start sites (TSSs) with limited co-occupancy by its catalytic microprocessor partner DROSHA. Acute DGCR8 depletion triggered a rapid genome-wide reduction in nascent RNA synthesis as measured by TT-seq, whereas PRO-seq revealed only modest changes in Pol II occupancy and no significant alteration in promoter-proximal pausing, suggesting that DGCR8 primarily supports transcriptional output rather than Pol II pausing. Consistently, TT-seq/PRO-seq ratios were broadly reduced following DGCR8 depletion, whereas acute DROSHA depletion produced the opposite effect. Mechanistically, proteomic and biochemical analyses identified DGCR8 interactions with Enhancer of Rudimentary Homolog (ERH) and the elongation factor SPT5. DGCR8 depletion reduced ERH and SPT5 chromatin occupancy, while acute ERH depletion similarly diminished SPT5 chromatin association and nascent transcription. Together, these findings identify a non-canonical DGCR8-ERH-SPT5 regulatory module that sustains global nascent transcription independently of the canonical DGCR8-DROSHA Microprocessor complex.