Isolation and Characterization of Human Casein Kinase I
(CKI), a Novel Member of the CKI Gene Family (*)
- Kimberly J. Fish(1)(2),
- Aleksandra Cegielska(1)(2),
- Michael E. Getman(4)(5),
- Gregory M. Landes(4) and
- David M. Virshup(1)(2)(3)(§)
- From the (1) Program in Human Molecular Biology and Genetics,
- (2)Department of Oncological Science, Division of Molecular Biology and Genetics, and
- (3)Department of Pediatrics, University of Utah, Salt Lake City, Utah 84112,
- (4)Department of Human Genetics, Integrated Genetics, Inc., Framingham, Massachusetts 01701, and the
- (5)Worcester Polytechnic Institute, Worcester, Massachusetts 01609
- § To whom correspondence should be addressed: Program in Human Molecular Biology and Genetics, University of Utah, Bldg. 533, Rm. 4420A, Salt Lake City, UT 84112. Internet: virshup{at}gene1.med.utah.edu.
Abstract
The casein kinase I (CKI) gene family is a rapidly enlarging group whose members have been implicated in the control of cytoplasmic
and nuclear processes, including DNA replication and repair. We report here the cloning and characterization of a novel isoform
of CKI from a human placental cDNA library. The cDNA for this isoform, hCKI
, predicts a basic polypeptide of 416 amino acids and a molecular mass of 47.3 kDa. It encodes a core kinase domain of 285
amino acids and a carboxyl-terminal tail of 123 amino acids. The kinase domain is 53-98% identical to the kinase domains of
other CKI family members and is most closely related to the 
isoform. Localization of the hCKI
gene to chromosome 22q12-13 and the hCKI
gene to chromosome 17q25 confirms that these are distinct genes in the CKI family. Northern blot analysis shows that hCKI
is expressed in multiple human cell lines. Recombinant hCKI
is an active enzyme that phosphorylates known CKI substrates including a CKI-specific peptide substrate and is inhibited
by CKI-7, a CKI-specific inhibitor. A budding yeast isoform of CKI, HRR25, has been implicated in DNA repair responses. Expression
of hCKI
but not hCKIα rescued the slow-growth phenotype of a Saccharomyces cerevisiae strain with a deletion of HRR25. Human CKI
is a novel CKI isoform with properties that overlap those of previously described CKI isoforms.
Footnotes
-
↵* This research was supported in part by National Institutes of Health Grant R01 AI31657 and the Primary Children's Medical Foundation (to D. M. V.). National Cancer Institute Grant 5 P30 CA42014 subsidized a portion of the costs of oligonucleotide and peptide synthesis. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank
/EMBL Data Bank with accession number(s) L37043, (hCKI
) and L37042 (hCKIα2).
-
↵1 The abbreviations used are:
- hCKI
-
human casein kinase I
- bp
-
base pair
- CKI
-
casein kinase I
, PAGE, polyacrylamide gel electrophoresis
- kb
-
kilobase pair
- FLpter%
-
fractional length from p terminus.
- hCKI
-
↵2M. Hoekstra, personal communication.
-
↵3K. J. Fish and D. M. Virshup, unpublished results.
