Human ribosomal protein L7 carries two nucleic acid-binding domains with distinct specificities

Protein L7 is associated with the large subunit of eukaryotic ribosomes tha t can act as a co-regulator of nuclear receptor-mediated transcription. In this study we show that L7 carries in addition to the known N-terminal nucl eic acid-binding domain (NBD 1) a second one (NBD 2) which maps to the 50 C -terminal amino acids of the protein. The amino acid sequence of this regio n does not contain any of the known nucleic acid binding motifs; thus, NBD 2 may represent a new class of nucleic acid-binding protein motifs. NBD 2 i s conserved in all known eukaryotic L7 homologs, whereas NBD 1 is only pres ent in mammalian L7. Binding studies show that NBD 2 is functionally differ ent from NBD 1 in that it binds preferentially to 28S rRNA, suggesting that NBD 2 is involved in the attachment of protein L7 to the large ribosomal s ubunit, Potential functions of NBD 1 and NBD 2 in translational and nuclear receptor-mediated transcriptional control are discussed. (C) 1999 Academic Press.