Identification and characterisation of a novel human RNA-binding protein

The processing of heterogeneous nuclear RNA (hnRNA) into a mature message occurs within a number of different nuclear ribonucleoprotein (RNP) complexes which bind to the hnRNA and provide the machinery for these modifying events. Although some components of the nuclear RNP complexes have been isolated, many remain to be elucidated. We report here the isolation of a novel human nucleic-acid-binding protein isolated by screening a lambda gt11 expression library with an oligodeoxyribonucleotide probe. The complete cDNA clone (E5.1) is homologous to a recently published murine sequence. The human gene encodes a ubiquitously expressed mRNA sequence with a putative open reading frame of 305 amino acids and contains a number of domains found in well characterised RNA-binding proteins. The E5.1-derived RNA recognition motif (RRM) is phylogenetically most related to the hnRNP C protein, a component of heterogeneous nuclear RNP particles which participates in mRNA splicing in vitro. E5.1 may, therefore, represent a novel gene, encoding a protein involved in processing of precursor RNAs into mature mRNA.