Cloning and characterization of DYRK1B, a novel member of the DYRK family of protein kinases

The DYRK1A gene on human chromosome 21 encodes a protein kinase presumed to be involved in the pathogenesis of mental retardation in Down's syndrome. Here we describe a highly similar homolog, DYRK1B, which is, in contrast to DYRK1A, predominately expressed in muscle and testis. The human DYRK1B gen e was mapped to chromosome 19 (19q12-13.11) by radiation hybrid analysis. T he amino acid sequences of DYRK1A and DYRK1B are 84% identical in the N-ter minus and the catalytic domain but show no extended sequence similarity in the C-terminal region. DYRK1B contains all motifs characteristic for the DY RK family of protein kinases, In addition, the sequence comprises a biparti te nuclear localization motif. A green fluorescent protein (GFP) fusion pro tein of DYRK1B was found mainly in the nucleus of transfected COS-7 cells. These data suggest that DYRK1B is a muscle- and testis-specific isoform of DYRK1A and is involved in the regulation of nuclear functions. (C) 1999 Aca demic Press.