Nucleolar transcription factor hUBF contains a DNA-binding motif with homology to HMG proteins.

The eukaryotic upstream binding factor (UBF), recognizes the ribosomal RNA gene promoter and activates transcription mediated by RNA polymerase I through cooperative interactions with the species-specific factor, SL1. Isolation of complementary DNA clones and sequence analysis reveals similarities between DNA binding domains of human UBF (hUBF) and high mobility group (HMG) protein 1. Expression, cellular localization and in vitro transcription studies establish that cloned hUBF encodes a nucleolar factor that binds specifically to the upstream control element and core of the rRNA gene promoter to activate transcription in a binding site-dependent manner.