CDNA CLONING AND CHROMOSOMAL MAPPING OF GENES ENCODING NOVEL PROTEIN-KINASES TERMED PKU-ALPHA AND PKU-BETA, WHICH HAVE NUCLEAR-LOCALIZATIONSIGNAL

We have cloned cDNAs for novel serine/threonine protein kinases (PK), termed PKU-alpha and PKU-beta, by screening a bacteriophage expression library for kinase activity. Sequence analysis of PKU-alpha and PKU-b eta genes revealed that their open reading frames (ORF) were 2151 and 2361 nucleotides (nt) encoding polypeptides of 727 and 787 amino acid (aa) residues, respectively. The deduced aa sequences of PKU-alpha and PKU-beta contained typical serine/threonine PK domains at the C-termi nal region and were 86% identical to each other, indicating that they belong to the same PK family. Northern analysis reveals that they are expressed in nearly all human tissues and in cultured cells. The genes for PKU-alpha and PKU-beta were mapped to chromosome 17q23 and 8p12-p 22, respectively, by fluorescence in situ hybridization. The proteins encoded by both cDNAs contain a putative nuclear localization signal ( NLS) in their N-terminal region. These signals are likely to function in nuclear localization. Glutathione S-transferase (GST)-fusions to re gions of PKU-alpha and beta containing the NLS were efficiently locali zed to the nucleus. In addition, PKU-beta transiently expressed in COS -1 cells was predominantly nuclear. PKU-alpha and PKU-beta differ: a c onsensus sequence for a nt binding motif is present near the NLS of PK U-beta. These results suggest that PKU-alpha and beta may phosphorylat e serine and/or threonine residues on similar proteins, but their acti vities are regulated through distinct interactions with a nuclear comp onent. (C) 1997 Elsevier Science B.V.