This family represents U3 small nucleolar RNA-associated protein 25 (UTP25), a DEAD-box RNA helicase-like protein component of the ribosomal small subunit processome for the biogenesis of ribosomes, which functions in pre-ribosomal RNA (pre-rRNA) processing. U3 small nucleolar RNA-associated protein 25 homologue (also known as Digestive organ expansion factor (DEF)) from animals is essential for embryonic development in part through the regulation of p53 pathway and controls the expansion growth of digestive organs and liver [, , ]. It is though to be also involved in the sympathetic neuronal development. UTP25 mediates, with CAPN3, the proteasome-independent degradation of p53/TP53 [, ].Protein NUCLEOLAR FACTOR 1 from Arabidopsis thaliana (Nof1) is also included in this group. This protein is involved in the control of rRNA expression, embryo development and female gametogenesis [].
