InterPro domain: IPR006630

Human Ro ribonucleoproteins (RNPs) are composed of one of the four small Y RNAs and at least two proteins, Ro60 and La. The La protein is a 47kDa polypeptide that frequently acts as an autoantigen in systemic lupus erythematosus and Sjogren's syndrome [ 1 ]. In the nucleus, La acts as a RNA polymerase III (RNAP III) transcription factor, while in the cytoplasm, La acts as a translation factor [ 2 ]. In the nucleus, La binds to the 3'UTR of nascent RNAP III transcripts to assist in folding and maturation [ 3 ]. In the cytoplasm, La recognises specific classes of mRNAs that contain a 5'-terminal oligopyrimidine (5'TOP) motif known to control protein synthesis [ 4 ]. The specific recognition is mediated by the N-terminal domain of La, which comprises a La motif and a RNA recognition motif (RRM). The La motif adopts an alpha/beta fold that comprises a winged-helix motif [ 5 ].

Homologous La domain-containing proteins have been identified in a wide range of organisms except Archaea, bacteria and viruses [ 6 ].

1. A peptide from autoantigen La blocks poliovirus and hepatitis C virus cap-independent translation and reveals a single tyrosine critical for La RNA binding and translation stimulation. J. Virol. 78, 3763-76
2. Differential phosphorylation and subcellular localization of La RNPs associated with precursor tRNAs and translation-related mRNAs. Mol. Cell 12, 1301-7
3. Structural analysis of cooperative RNA binding by the La motif and central RRM domain of human La protein. Nat. Struct. Mol. Biol. 11, 323-9
4. Posttranscriptional generation of macromolecular complexes. Mol. Cell 12, 1347-9
5. La gets its wings. Nat. Struct. Mol. Biol. 11, 303-5
6. A yeast RNA binding protein that resembles the human autoantigen La. J. Mol. Biol. 245, 81-5