Mechanism of Bruton's tyrosine kinase-mediated recruitment and regulation of TFII-I.
TFII-I is a ubiquitously expressed multifunctional transcription factor with broad biological roles in transcription and signal transduction in a variety of cell types. We and others have shown that TFII-I can interact physically and functionally with Bruton's tyrosine kinase (Btk), a hematopoietic non-receptor protein tyrosine kinase that is critical for B lymphocyte development. Although TFII-I-Btk interactions are impaired in B cells from X-linked immunodeficient mice, the precise molecular determinants governing TFII-I-Btk complex formation remain unknown. To this end, we have conducted a structural analysis of TFII-I-Btk interactions by using a panel of TFII-I mutants. These studies have revealed that a region within the N-terminal 90 amino acids of TFII-I, which includes a putative leucine zipper motif, is primarily responsible for its interaction with Btk. Mutations in the leucine zipper region itself were not sufficient to abrogate binding of TFII-I to Btk, suggesting that regions/residues outside the leucine zipper are responsible for such interactions. Because the first 90 amino acids of TFII-I are required for its dimerization, we propose that Btk tethers TFII-I to the cytoplasm by preventing its dimerization and its subsequent nuclear localization. We further examined the requirement of tyrosine phosphorylation for TFII-I-Btk complex formation. Our data showed that Src-dependent tyrosine phosphorylation sites in TFII-I are not targeted by Btk, suggesting that multiple kinases can independently target TFII-I via distinct signaling pathways. Our results provide a beginning step toward understanding the functional importance of the TFII-I-Btk pathway in B cell signaling and gene expression.
Sacristán
Catarina
C
Department of Pathology, Program in Immunology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Tussié-Luna
María Isabel
MI
Logan
Sheila M
SM
Roy
Ananda L
AL
D000077329:Agammaglobulinaemia Tyrosine Kinase; D020816:Amino Acid Motifs; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology; D015153:Blotting, Western; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D019281:Dimerization; D005347:Fibroblasts / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D005982:Glutathione Transferase / Q000378:metabolism; D007930:Leucine / Q000737:chemistry; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D009154:Mutation; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics; D015398:Signal Transduction; D019473:Transcription Factors, TFII / Q000096:biosynthesis* / Q000235:genetics*; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
D000596:Amino Acids; C486330:Gtf2i protein, mouse; D020033:Protein Isoforms; D019473:Transcription Factors, TFII; D014443:Tyrosine; D008156:Luciferases; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse; D007930:Leucine