Jun N-terminal kinase activity and early growth-response factor-1 gene expression are down-regulated in Fanconi anemia group A lymphoblasts

Abstract

Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome characterized by cellular sensitivity to genotoxic agents. In recent years, FA proteins have been associated with different molecules involved in signal transduction, which has raised the interest in FA-dependent signaling pathways. Here, we report that the c-Jun N-terminal kinase (JNK) fails to phosphorylate in response to UV radiation and treatment with mitomycin C in FA lymphoblast cells derived from type A patients (FA-A). Furthermore, defective kinase activity seems to be specific for JNK, because extracellular signalregulated kinase (ERK) responded to the proper stimuli in FA-A cells. We also demonstrate that the early growthresponse factor-1 (Egr-1), a JNK downstream target gene that is normally induced by genotoxic stress, is not upregulated in UV IntroductionFanconi anemia (FA) is an autosomal recessive disease characterized by developmental abnormalities, progressive bone marrow failure, and cancer susceptibility. At the cellular level, FA cells are hypersensitive to DNA cross-linking agents such as mitomycin C (MMC) or diepoxybutane. 1,2 FA is a genetically heterogeneous disease, comprising at least 8 complementation groups: FA-A, -B, -C, -D1, -D2, -E, -F and -G, the FA-A group being the most frequently represented in these patients. 3,4 Seven FA-associated genes have been cloned to date, and their products were found to interact with DNA damage-response proteins, including BRCA1, ATM, and NBS1. [5][6][7] In line with this, it has been described that FA proteins may be involved in the process of repairing chromosome defects that occur during homologous recombination. 5 A complex of 5 FA proteins (FANCA, FANCC, FANCE, FANCF, and FANCG) triggers the monoubiquitination of the FANCD2 protein and its interaction with BRCA1 in response to DNA damage. 6 BRCA1 plays an important role in mediating cell cycle arrest, apoptosis, and cellular responses to DNA damage signals. 8,9 Recently it has been shown that BRCA1 is cleaved by caspase-3 during UV-induced apoptosis, which produces a C-terminal fragment that triggers an apoptotic response through activation of c-Jun N-terminal kinase (JNK) and GADD45. 10 Consistently, phosphorylation activity of JNK is abrogated in breast cancer cells after blockade of BRCA1 expression with specific ribozymes, indicating that JNK is a downstream target of BRCA1. 11 Additionally, FANC proteins exhibit functions besides their role in the complex. To this end, a number of FANCC-dependent molecular mechanisms have been suggested to ensure the survival of hematopoietic cells. Notably, FANCC is involved in the activation of signal transducer and activator of transcription-1 (STAT1) through growth factor receptors, 12 it cooperates with heat-shock protein 70 (Hsp70) to suppress the activity of proapoptotic interferon-inducible double-stranded RNA-dependent protein kinase (PKR), 13 and binds to glutathione S-transferase P1-1 (GSTP1), inducing the detoxification of by-products of oxidative stress. 14 Interest...

Defective binding of transcriptional repressor ZEB via DNA methylation contributes to increased constitutive levels of p73 in Fanconi anemia cells

“…Transcriptional activation of p73 is mediated at least in part by Egr1 and E2F1 proteins [13,14]. We previously described that constitutive expression of Egr1 is reduced in FA-A cells [15]. Here, we confirmed and extended this finding by analyzing the capacity of Egr1 to bind to the p73 promoter in FA-A cells.…”

Fibroblasts from long-lived mutant mice show diminished ERK1/2 phosphorylation but exaggerated induction of immediate early genes

“…It has been shown recently that the increase in expression of egr-1 is important for the resistance of cells from apoptotic stimuli [23]. We therefore investigated whether dwarf and normal cells differ in expression of this transcription factor in response to H 2 O 2 exposure.…”

Elevated levels of IL-1β in Fanconi anaemia group A patients due to a constitutively active phosphoinositide 3-kinase-Akt pathway are capable of promoting tumour cell proliferation

“…However, not every aspect of the cellular FA phenotype could be explained through the formation of this nuclear complex. A growing amount of evidence points to a role of FANCC and FANCA in the signal transduction pathways leading to the inhibition of apoptosis and the promotion of cell survival [2][3][4]. Mutation analysis of FANCC identified different domains responsible for its separated nuclear and cytoplasmic functions [5].…”

“…Mutation analysis of FANCC identified different domains responsible for its separated nuclear and cytoplasmic functions [5]. The deficiency in different FANC proteins has been associated with alterations in the activation of several transduction pathways [2,6,7]. A large effort has been made to discover alterations leading to the haematological problems of these patients.…”