Molecular characterization of a mouse heterogeneous nuclear ribonucleoprotein D-like protein JKTBP and its tissue-specific expression

The human DNA- and RNA-binding protein JKTBP is a new member of heterogeneo us nuclear ribonucleoproteins (hnRNPs) that are involved in mRNA biogenesis . We cloned and characterized a mouse homolog and studied its expression in mouse tissues. The cDNA encoded a 301-residue polypeptide. There is only a single amino acid difference between the mouse and human sequences. Northe rn blotting indicated ubiquitous but varied expressions of approximately 1. 4 and 2.8 kb mRNAs in various tissues. Immunoblotting indicated that the am ounts of protein of about 38 kDa were higher in the brain and testis than i n other tissues. An additional protein or about 53 KDa was found in the bra in and testis. Germ cell-deficient W/W-v mutant mice and aged mice had the reduced amounts of JKTBP in the testes. Immunohistochemical staining indica ted cell type-specific expression of JKTBP in tissues: neurons and spermato cytes displayed strong signal intensities. The signals were confined to the nucleus. The amount of 38 kDa JKTBP was estimated to be approximately 1.3 x 10(7) molecules per HL-60 cell. These results indicate that JKTBP is an a bundant, highly conserved nuclear protein. (C) 2000 Elsevier Science B.V. A ll rights reserved.