| Protein kinases, which play an important role in cell signing transduction, is a kind of enzymes that can phosphorylate lots of proteins in the organism. There are two subvisions in the protein kinase superfamily, serine/threonine kinase and tyrosine kinase. Casein kinase are ubiquitous in eukaryotic organisms and yeasts, they belong to the serine/threonine kinase family and contain CK1 and CK2 subfamilies. Casein kinase I (CKI) was one of the first serine/threonine protein kinase activities to be isolated and characterised. Since then, mammalian CKI subfamilies designed α,β,γ,δ and ε have been cloned and characterized, γ1, γ2, γ3 are the members of CK1γ subfamily. Besides serine/threonine kinase and tyrosine kinase, there exist the dual-specificity protein kinases (DSPK), which possess both serine/threonine kinase and tyrosine kinase activity. From a human fetal brain cDNA library, we isolated two novel human kinase genes, CK1γ1L2 and PDIK1L. CK1γ1L2 is a new isoform of CK1γ1. It contained 1756 bp and encoded a putative protein of 438 amino acids. The nucleotide and peptide sequences showed 93% and 94% identity with the rat CK1γ1. The gene CK1γ1L2 located in human chromosome 15q22.31 and contained 11 exons. The results of subcelluar localisation showed that CK1γ1L2 protein mainly located in the cell nucleus. The expression of CK1γ1L2 could be detected in brain, liver, spleen, peripheral blood leukocyte, kidney, lung, small intestine, ovary, testis and prostate, as well as heart and skeletal muscle according to the Northern Blot and RT-PCR analysis results. In addition, the results displayed that CK1γ1L2 expressed in ovarian carcinoma, colon carcinoma, prostatic adenocarcinoma, lung carcinoma and breast adenocarcinoma. It suggests CK1γ1L2 maybe a gene which associate with tumors.PDIK1L contained 4301 bp and encoded a putative protein of 341 amino acids. Bioinformaic analysis represented that the 341-aa peptide showed over 90% homologous with both serine/threonine kinase and tyrosine kinase catalytic domain and 69% homologous with the human CLIK1, which act as the interacting kinase of the PDZ-LIM protein CLP-36. Therefore, approved by the HUGO Gene Nomenclature Committee, it was named PDIK1L, PDLIM1 interacting kinase 1 like. The gene PDIK1L located in human chromosome 1p36.11 and contained 4 exons. Results of subcelluar localisation showed that PDIK1L protein also located in the cell nucleus. According to the PT-PCR, we found PDIK1L expressed in various tissues such as pancreas, prostate, thymus and spleen. Expression signal of the mRNA sequence lies in the middle part (1781-2200) was detected in peripheral blood leukocyte, colon, small intestine, ovary and testis while expression signal of the mRNA sequence close to the 3'end(3296-3724) was detected in liver, kidney, heart, brain and planceta, maybe the existence of different PDIK1L transcripts should responsible for the tissue-difference expression within the same gene. Kinase assay results demonstrate the serine/threonine kinase activity of PDIK1L. Two-yeast hybrid revealed that a potential glutamine receptor, GRINL1A, maybe associate with PDIKL1A, co-immunoprecipitation confirmed further the association between the two proteins. It may provied more proof and clue for the next research of the function of PDIK1L.
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