Functional analysis of a dominant negative mutation of interferon regulatory factor 5.
BACKGROUND
Interferon regulatory factor (IRF) family members have been implicated as critical transcription factors that function in immune response, hematopoietic differentiation and cell growth regulation. Activation of IRF-5 results in the production of pro-inflammatory cytokines such as TNFalpha, IL6 and IL12p40, as well as type I interferons.


RESULTS
In this study, we identify a G202C (position relative to translation start codon) missense-mutation transcript of IRF-5 in transformed B and T cell lines, which were either infected or non-infected by viruses, and peripheral blood from ATL or CLL patients. The mutated transcript encodes a novel protein in which the sixty-eighth amino acid, Alanine, is substituted by Proline (IRF-5P68) in the DNA binding domain of IRF-5. IRF-5P68 phenotype results in a complete loss of its DNA-binding activity and functions as a dominant negative molecule through interacting with wild type IRF-5. Co-expression of IRF-5P68 inhibits MyD88-mediated IRF-5 transactivation. Moreover, Toll-like receptor (TLR)-dependent IL6 and IL12P40 production induced by lipopolysaccharide (LPS), R837 or CpG ODN 1826 was reduced in IRF-5 (P68) expressing cells as compared to the control cells.


CONCLUSIONS
IRF-5P68 acts as a dominant negative regulator that interferes with IRF-5-mediated production of pro-inflammatory cytokines. The functional characterization of the novel IRF-5 mutant in transformed B and T cell lines and in ATL and CLL patients may lead to a better understanding of the role of these transcriptional regulators in hematopoietic malignancies.
Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada.
Long
L
Yang
Tiejun
T
Zhao
Xiaoliu
X
Shi
Peyman
P
Nakhaei
Yunling
Y
Wang
Qiang
Q
Sun
John
J
Hiscott
Rongtuan
R
Lin
D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D024202:Electrophoretic Mobility Shift Assay; D005799:Genes, Dominant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D050835:Interferon Regulatory Factors / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018664:Interleukin-12 / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D019169:Jurkat Cells; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000097:blood / Q000473:pathology; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000097:blood / Q000473:pathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008214:Lymphocytes / Q000378:metabolism / Q000473:pathology; D051379:Mice; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D050505:Mutant Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation
C431713:IRF5 protein, human; D050835:Interferon Regulatory Factors; D015850:Interleukin-6; C498178:Irf5 protein, mouse; D008070:Lipopolysaccharides; D050505:Mutant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D018664:Interleukin-12