Vol. 13, Issue 10, 3683-3695, October 2002

A Novel Conserved RNA-binding Domain Protein, RBD-1, Is Essential For Ribosome Biogenesis

Petra Björk,^* Göran Baurén,^* ShaoBo Jin,^* Yong-Guang Tong, Thomas R. Bürglin, Ulf Hellman, and Lars Wieslander^*§

 ^*Department of Molecular Biology and Functional Genomics, Stockholm University, SE-106 91 Stockholm, Sweden;  Department of Biosciences at Novum and Center for Genomics and Bioinformatics, Karolinska Institutet, SE-141 04 Huddinge, Sweden; and  Ludwig Institute for Cancer Research, SE-751 24 Uppsala, Sweden

Synthesis of the ribosomal subunits from pre-rRNA requires a large number of trans-acting proteins and small nucleolar ribonucleoprotein particles to execute base modifications, RNA cleavages, and structural rearrangements. We have characterized a novel protein, RNA-binding domain-1 (RBD-1), that is involved in ribosome biogenesis. This protein contains six consensus RNA-binding domains and is conserved as to sequence, domain organization, and cellular location from yeast to human. RBD-1 is essential in Caenorhabditis elegans. In the dipteran Chironomus tentans, RBD-1 (Ct-RBD-1) binds pre-rRNA in vitro and anti-Ct-RBD-1 antibodies repress pre-rRNA processing in vivo. Ct-RBD-1 is mainly located in the nucleolus in an RNA polymerase I transcription-dependent manner, but it is also present in discrete foci in the interchromatin and in the cytoplasm. In cytoplasmic extracts, 20-30% of Ct-RBD-1 is associated with ribosomes and, preferentially, with the 40S ribosomal subunit. Our data suggest that RBD-1 plays a role in structurally coordinating pre-rRNA during ribosome biogenesis and that this function is conserved in all eukaryotes.