UBF-1 binds directly to the CORE and UCE elements of the ribosomal DNA promoter. This binding is mediated by the HMG boxes (primarily HMG box1). Phosphorylation may play a role in the modulation of UBF's DNA binding activity, as well as in subsequent steps. UBF is thought to bind DNA in a conformation specific manner (as opposed to a sequence specific manner). The binding of UBF to the minor groove of DNA induces strong DNA bending.