Heterogeneous nuclear ribonucleoproteins (hnRNPs): an emerging family of autoantigens in rheumatic diseases.

In eukaryotic cells, mature mRNA molecules are produced through the extensive post-transcriptional processing of primary transcripts assembled in ribonucleoprotein complexes. Twenty polypeptides, termed heterogeneous nuclear ribonucleoproteins or hnRNPs, have been identified as the major components of such complexes. Although these proteins were identified more than 30 years ago, their role in RNA metabolism is just beginning to emerge. In contrast to previous models that ascribed to hnRNPs a mere structural function, recent data suggest a direct involvement in several aspects of the RNA life, such splicing, export of the mature mRNAs to the cell cytoplasm and translation. In addition, a growing body of evidence points to hnRNPs as an important target of the autoimmune response in rheumatic diseases. The present paper will review some of the most relevant data concerning the structure, function and autoantigenic properties of the hnRNPs.