ARGLU1 is a dual-function regulator of gene expression that acts as both a transcriptional coactivator and alternative splicing modulator 1. As a coactivator, ARGLU1's glutamate-rich C-terminus cooperates with the Mediator complex to enhance nuclear receptor-induced transcription, including glucocorticoid receptor and estrogen receptor signaling 12. Its arginine-rich N-terminus binds pre-mRNA and spliceosome components to regulate cassette exon splicing events 1. ARGLU1 uniquely undergoes autoregulation through binding its own pre-mRNA, which generates a stable intronic sequence RNA (sisRNA) that promotes ARGLU1 localization to nuclear speckles and enhances its splicing activity 3. ARGLU1 is essential for CNS development; deletion causes widespread alternative splicing defects, particularly in neurogenesis genes, leading to p53-dependent apoptosis and microcephaly 4. Additionally, ARGLU1 enhances promoter-proximal RNA polymerase II pausing and stimulates DNA damage repair, mechanisms exploited by cancer cells for chemotherapy resistance 5. In head and neck carcinoma, DTL-mediated degradation of ARGLU1 activates oncogenic Notch signaling 6. ARGLU1 also functions as an antiviral restriction factor by repressing viral gene expression 7, highlighting its critical roles in development, stress responses, and disease.