The hnRNPs (heterogeneous nuclear ribonucleoproteins) are RNA binding proteins associated with pre-mRNAs in the nucleus, that form complexes with heterogeneous nuclear RNA (hnRNA).
However, since most mature RNA is exported from the nucleus relatively quickly, most RBPs in the nucleus exist as complexes of protein and pre-mRNA called heterogeneous ribonucleoprotein particles (hnRNPs). 
