TY - JOUR
T1 - Physical and functional characterization of the genetic locus of IBtk, an inhibitor of Bruton's tyrosine kinase
T2 - Evidence for three protein isoforms of IBtk
AU - Spatuzza, Carmen
AU - Schiavone, Marco
AU - Di Salle, Emanuela
AU - Janda, Elzbieta
AU - Sardiello, Marco
AU - Fiume, Giuseppe
AU - Fierro, Olga
AU - Simonetta, Marco
AU - Argiriou, Notis
AU - Faraonio, Raffaella
AU - Capparelli, Rosanna
AU - Quinto, Ileana
AU - Scala, Giuseppe
N1 - Funding Information:
We are grateful to Dr P. Schwartzberg, NHGRI-NIH for helping in generating the Ibtk−/− mice, Dr N. Zambrano for the IBTK siRNA clone. We thank Dr M. Rocchi, Institute of Biomedical Biotechnologies-CNR, 70100 Bari, Italy, for providing the genomic DNA of Pongo pygmaeus and Pan troglodytes. This work was supported by grants from the Associazione Italiana per la Ricerca sul Cancro (AIRC), MIUR-PRIN, MIUR-FIRB, ISS to G.S. Funding to pay the Open Access publication charges for this article was provided by Department of Experimental and Clinical Medicine, University of Catanzaro, Italy.
PY - 2008/8
Y1 - 2008/8
N2 - Bruton's tyrosine kinase (Btk) is required for B-cell development. Btk deficiency causes X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Btk lacks a negative regulatory domain and may rely on cytoplasmic proteins to regulate its activity. Consistently, we identified an inhibitor of Btk, IBtk, which binds to the PH domain of Btk and down-regulates the Btk kinase activity. IBtk is an evolutionary conserved protein encoded by a single genomic sequence at 6q14.1 cytogenetic location, a region of recurrent chromosomal aberrations in lymphoproliferative disorders; however, the physical and functional organization of IBTK is unknown. Here, we report that the human IBTK locus includes three distinct mRNAs arising from complete intron splicing, an additional polyadenylation signal and a second transcription start site that utilizes a specific ATG for protein translation. By northern blot, 5′RACE and 3′RACE we identified three IBTKα, IBTKβ and IBTKγ mRNAs, whose transcription is driven by two distinct promoter regions; the corresponding IBtk proteins were detected in human cells and mouse tissues by specific antibodies. These results provide the first characterization of the human IBTK locus and may assist in understanding the in vivo function of IBtk.
AB - Bruton's tyrosine kinase (Btk) is required for B-cell development. Btk deficiency causes X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Btk lacks a negative regulatory domain and may rely on cytoplasmic proteins to regulate its activity. Consistently, we identified an inhibitor of Btk, IBtk, which binds to the PH domain of Btk and down-regulates the Btk kinase activity. IBtk is an evolutionary conserved protein encoded by a single genomic sequence at 6q14.1 cytogenetic location, a region of recurrent chromosomal aberrations in lymphoproliferative disorders; however, the physical and functional organization of IBTK is unknown. Here, we report that the human IBTK locus includes three distinct mRNAs arising from complete intron splicing, an additional polyadenylation signal and a second transcription start site that utilizes a specific ATG for protein translation. By northern blot, 5′RACE and 3′RACE we identified three IBTKα, IBTKβ and IBTKγ mRNAs, whose transcription is driven by two distinct promoter regions; the corresponding IBtk proteins were detected in human cells and mouse tissues by specific antibodies. These results provide the first characterization of the human IBTK locus and may assist in understanding the in vivo function of IBtk.
UR - https://www.scopus.com/pages/publications/48349089940
U2 - 10.1093/nar/gkn413
DO - 10.1093/nar/gkn413
M3 - Article
C2 - 18596081
AN - SCOPUS:48349089940
SN - 0305-1048
VL - 36
SP - 4402
EP - 4416
JO - Nucleic acids research
JF - Nucleic acids research
IS - 13
ER -