Two-hybrid cloning identifies hnRNP A/B0 as an interactive protein of hnRNP L

The heterogeneous nuclear ribonucleoprotein L (hnRNP L) is one of the major pre-mRNA binding proteins. It is composed of 558 amino acid residues and contains four loosely conserved RNP-concensus RNA-binding domains. hnRNP L is an abundant nuclear protein and shuttles between nucleus and cytoplasm. As a first step to investigate the functions of hnRNP L, we searched for hnRNP L-interacting proteins in a human liver cDNA library using a yeast two-hybrid screening system. One of the cDNA clones (GeneBank accession number AK097657) consists of 332 amino acid residues and is identical to human hnRNP A/B protein (GeneBank accession number XM_038946) except for a 47-residue insertion, presumably produced by alternative RNA splicing. This protein, named hnRNP A/B0, contains two RNP-CS RNA-binding domains at its N-terminal half and glycine-rich domain in the C-terminal region. Here, we report that hnRNP L specifically interacts with ImRNP A/B0 in yeast two-hybrid system.