Rix1 is a nucleoplasmic particle involved in rRNA processing/ribosome assembly [1,2]. It associates with two other proteins, Ipi1 and Ipi3, to form the RIX1 complex that allows Rea1 - the AAA ATPase - to associate with the 60S ribosomal subunit. More than 170 assembly factors are involved in the construction and maturation of yeast ribosomes, and after these factors have completed their function they need to be released from the pre-ribosomes. Rea1 induces the release of the assembly protein complex in a mechanical fashion [3]. This family is usually associated with NUC202, Pfam:PF08166.

1: Insights into the evolution of the nucleolus by an analysis of its protein domain repertoire. Staub E, Fiziev P, Rosenthal A, Hinzmann B; Bioessays 2004;26:567-581. PMID:15112237

2: 60S pre-ribosome formation viewed from assembly in the nucleolus until export to the cytoplasm. Nissan TA, Bassler J, Petfalski E, Tollervey D, Hurt E; EMBO J. 2002;21:5539-5547. PMID:12374754

3: The Rea1 tadpole loses its tail. Talkish J, Woolford JL Jr; Cell. 2009;138:832-834. PMID:19737511