Identification and Characterization of a Novel Related Adhesion Focal Tyrosine Kinase (RAFTK) from Megakaryocytes and Brain (*)
- Shalom Avraham(§),
- Roanna London,
- Yigong Fu,
- Setsuo Ota,
- Dan Hiregowdara,
- Junzhi Li,
- Shuxian Jiang,
- Linda M. Pasztor(1),
- Robert A. White(1),
- Jerome E. Groopman and
- Hava Avraham
- From the Division of Hematology/Oncology, Deaconess Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215 Section of Genetics, Children's Mercy Hospital, University of Missouri School of Medicine, Kansas City, Missouri 64108
- § To whom correspondence should be addressed: Div. of Hematology/Oncology, Deaconess Hospital, One Deaconess Rd., Boston, MA 02215. Tel.: 617-632-0524; Fax: 617-424-6237.
Abstract
We have isolated a cDNA encoding a novel human intracytoplasmic tyrosine kinase, termed RAFTK (for a related adhesion focal
tyrosine kinase). In addition, we have cloned and characterized the murine homolog of the human RAFTK cDNA. Comparison of the deduced amino acid sequences of human RAFTK and murine Raftk cDNAs revealed 95% homology, indicating that RAFTK is highly conserved between these species. The RAFTK cDNA clone, encoding a polypeptide of 1009 amino acids, has closest homology (48% identity, 65% similarity) to the focal
adhesion kinase (pp125
). Comparison of the deduced amino acid sequences also indicates that RAFTK, like pp125
, lacks a transmembrane region, myristylation sites, and SH2 and SH3 domains. In addition, like pp125
, RAFTK contains a kinase domain flanked by large N-terminal (426 residues) and C-terminal (331 residues) domains, and the
C-terminal region contains a predicted proline-rich stretch of residues. In fetal tissues, RAFTK expression was abundant in
brain, and low levels were observed in lung and liver. In adult tissues, it was less restricted, indicating that RAFTK expression
is developmentally up-regulated. Expression of RAFTK was also observed in human CD34
marrow cells, primary bone marrow megakaryocytes, platelets, and various areas of brain. The human RAFTK gene was assigned to human chromosome 8 using genomic DNAs from human/rodent somatic cell hybrid lines. The mouse Raftk gene was mapped to chromosome 14, closely linked to gonadotropin-releasing hormone. Using specific antibodies for RAFTK,
a 
123-kDa protein from the human megakaryocytic CMK cell line was immunoprecipitated. Treatment of the megakaryocytic CMK cells
with thrombin caused a rapid induction of tyrosine phosphorylation of RAFTK protein. The structural features of RAFTK suggest
that it is a member of the focal adhesion kinase gene family and may participate in signal transduction in human megakaryocytes
and brain as well as in other cell types.
Footnotes
-
↵* This work was supported in part by National Institutes of Health Grants HL51456 and HL46668. 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.
This paper is dedicated to Ronald Ansin for his friendship and support for our research program.
-
↵1 The abbreviations used are:
- PCR
-
polymerase chain reaction
- bp
-
base pair(s)
- kb
-
kilobase pair(s)
- RFLP
-
restriction fragment length polymorphism
- RI
-
recombinant inbred
- FAK
-
focal adhesion kinase
- GST
-
glutathione S-transferase.
-
↵2 L. J. Maltais, D. P. Doolittle, A. L. Hillyard, J. N. Guidi, M. T. Davisson, and T. H. Roderick(1993) GBASE, the genomic data base of the mouse maintained at The Jackson Laboratory.
-
↵3 J. Li, personal communication.
-
- Received May 31, 1995.
- Revision received August 8, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
