fourth high mobility group (HMG)-box found in upstream-binding factor 1 (UBF1) and similar proteins
UBF1, also called UBTF, nucleolar transcription factor 1, or auto-antigen NOR-90, is a nucleolar transcription factor that recognizes the ribosomal RNA gene promoter and activates transcription mediated by RNA polymerase I through cooperative interactions with the transcription factor SL1/TIF-IB complex. It binds specifically to the upstream control element. UBF1 contains six HMG-box domains. This model corresponds to the fourth one.
Jiyao W et al.(2023). "The conserved domain database in 2023.",