SUPT4H1 is a conserved transcription elongation factor that functions as a component of the DSIF (DRB sensitivity-inducing factor) complex, which regulates RNA polymerase II transcription 1. As part of the DSIF complex, SUPT4H1 plays dual regulatory roles: it promotes promoter-proximal pausing by cooperating with the NELF complex to inhibit the elongation factor TFIIS, facilitating assembly of elongation-competent RNA polymerase II, and it positively regulates transcriptional elongation and mRNA capping 1. SUPT4H1 is ubiquitously expressed across tissues and is essential for global RNA synthesis; its depletion causes widespread reduction in cellular RNA rather than selective effects on specific transcripts 2. Clinically, biallelic SUPT4H1 variants cause a previously unrecognized autosomal recessive multisystem neurodevelopmental disorder featuring intellectual disability, dystonia, and skeletal abnormalities, with functional studies revealing disrupted transcriptional machinery and dysregulation of developmental gene networks 3. Additionally, SUPT4H1 expression dysregulation has been associated with multiple cancer types, including prostate and pancreatic cancer, suggesting roles in disease pathogenesis 45. However, therapeutic targeting of SUPT4H1 faces significant challenges due to its global transcriptional effects 2.