IRF5 is a target of BCR-ABL kinase activity and reduces CML cell proliferation.
Interferon regulatory factor 5 (IRF5) modulates the expression of genes controlling cell growth and apoptosis. Previous findings have suggested a lack of IRF5 transcripts in both acute and chronic leukemias. However, to date, IRF5 expression and function have not been investigated in chronic myeloid leukemia (CML). We report that IRF5 is expressed in CML cells, where it interacts with the BCR-ABL kinase that modulates its expression and induces its tyrosine phosphorylation. Tyrosine-phosphorylated IRF5 displayed reduced transcriptional activity that was partially restored by imatinib mesylate (IM). Interestingly, a mutant devoid of a BCR-ABL consensus site (IRF5(Y104F)) still presented significant tyrosine phosphorylation. This finding suggests that the oncoprotein phosphorylates additional tyrosine residues or induces downstream signaling pathways leading to further IRF5 phosphorylation. We also found that ectopic expression of IRF5 decreases the proliferation of CML cell lines by slowing their S-G2 transition, increasing the inhibition of BCR-ABL signaling and enhancing the lethality effect observed after treatment with IM, α-2-interferon and a DNA-damaging agent. Furthermore, IRF5 overexpression successfully reduced the clonogenic ability of CML CD34-positive progenitors before and after exposure to the above-indicated cytotoxic stimuli. Our data identify IRF5 as a downstream target of the BCR-ABL kinase, suggesting that its biological inactivation contributes to leukemic transformation.
Department of Clinical and Molecular Bio-Medicine, University of Catania, 85-95124 Catania, Italy.
Michele
M
Massimino
Maria Letizia
ML
Consoli
Maria
M
Mesuraca
Fabio
F
Stagno
Elena
E
Tirrò
Stefania
S
Stella
Maria Stella
MS
Pennisi
Chiara
C
Romano
Pietro
P
Buffa
Heather M
HM
Bond
Giovanni
G
Morrone
Laura
L
Sciacca
Francesco
F
Di Raimondo
Livia
L
Manzella
Paolo
P
Vigneri
D001549:Benzamides / Q000494:pharmacology / Q000633:toxicity; D002384:Catalysis; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005047:Etoposide / Q000494:pharmacology / Q000633:toxicity; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D050835:Interferon Regulatory Factors / Q000378:metabolism*; D016898:Interferon-alpha / Q000494:pharmacology; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology / Q000633:toxicity; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology / Q000633:toxicity; D015398:Signal Transduction / Q000187:drug effects; D015533:Transcriptional Activation; D014410:Tumor Stem Cell Assay
D001549:Benzamides; C431713:IRF5 protein, human; D050835:Interferon Regulatory Factors; D016898:Interferon-alpha; D010879:Piperazines; D011743:Pyrimidines; D005047:Etoposide; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases