Cloning and characterization of a heterogeneous nuclear ribonucleoprotein homolog from pearl oyster, Pinctada fucata.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) have fundamental roles in the post-transcriptional control of gene expression. Here, a cDNA encoding a presumed full-length RNA-binding protein was isolated from pearl oyster (Pinctada fucata) using reverse transcription-polymerase chain reaction with degenerate primers, and rapid amplification of cDNA ends. The full-length cDNA consists of 2737 bp with an open reading frame encoding a protein of 624 amino acids with a predicted molecular weight of 69 kDa and isoelectric point of 8.7. The putative pearl oyster RNA-binding protein presents a molecular organization close to the hnRNPs, namely an acidic N-terminal followed by three RNA-recognition motifs and a C-terminal that contains RG/RGG repeated motifs. When transfected HeLa cells, the Pf-HRPH (Pinctada fucata hnRNP homolog) gene expression product was found only in nuclei, revealing that it is a nuclear protein. The expression pattern was also investigated by quantitative real-time polymerase chain reaction, indicating that Pf-HRPH mRNA was abundantly expressed in gonad, gill, and viscera. As far as we know, the putative Pf-HRPH is the first hnRNP homolog cloned in mollusks. These data are significant for further study of the multiple functions of RNA-binding protein.