RNA recognition motif 1 in La autoantigen (La or LARP3) and similar proteins
This subfamily corresponds to the RRM1 of La autoantigen, also termed Lupus La protein, or La ribonucleoprotein, or Sjoegren syndrome type B antigen (SS-B), a highly abundant nuclear phosphoprotein and well conserved in eukaryotes. It specifically binds the 3'-terminal UUU-OH motif of nascent RNA polymerase III transcripts and protects them from exonucleolytic degradation by 3' exonucleases. In addition, La can directly facilitate the translation and/or metabolism of many UUU-3' OH-lacking cellular and viral mRNAs, through binding internal RNA sequences within the untranslated regions of target mRNAs. La contains an N-terminal La motif (LAM), followed by two RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). It also possesses a short basic motif (SBM) and a nuclear localization signal (NLS) at the C-terminus.