This gene encodes a member of the HMG-box DNA-binding protein family. The encoded protein plays a critical role in ribosomal RNA transcription as a key component of the pre-initiation complex, mediating the recruitment of RNA polymerase I to rDNA promoter regions. The encoded protein may also play important roles in chromatin remodeling and pre-rRNA processing, and its activity is regulated by both phosphorylation and acetylation. Alternatively spliced transcript variants encoding multiple isoforms have been observed for this gene. Pseudogenes of this gene are located on the short arm of chromosomes 3, 11 and X and the long arm of chromosome 11. Recognizes the ribosomal RNA gene promoter and activates transcription mediated by RNA polymerase I (Pol I) through cooperative interactions with the transcription factor SL1/TIF-IB complex. It binds specifically to the upstream control element and can activate Pol I promoter escape.