FANCJ protein is important for the stability of FANCD2/FANCI proteins and protects them from proteasome and caspase-3 dependent degradation.

David W Clark,Kaushlendra Tripathi,Komaraiah Palle,Josephine C Dorsman

doi:10.18632/oncotarget.5006

David W Clark, Kaushlendra Tripathi + Show 2 more

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https://doi.org/10.18632/oncotarget.5006

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Abstract

Fanconi anemia (FA) is a rare genome instability syndrome with progressive bone marrow failure and cancer susceptibility. FANCJ is one of 17 genes mutated in FA-patients, comprises a DNA helicase that is vital for properly maintaining genomic stability and is known to function in the FA-BRCA DNA repair pathway. While exact role(s) of FANCJ in this repair process is yet to be determined, it is known to interact with primary effector FANCD2. However, FANCJ is not required for FANCD2 activation but is important for its ability to fully respond to DNA damage. In this report, we determined that transient depletion of FANCJ adversely affects stability of FANCD2 and its co-regulator FANCI in multiple cell lines. Loss of FANCJ does not significantly alter cell cycle progression or FANCD2 transcription. However, in the absence of FANCJ, the majority of FANCD2 is degraded by both the proteasome and Caspase-3 dependent mechanism. FANCJ is capable of complexing with and stabilizing FANCD2 even in the absence of a functional helicase domain. Furthermore, our data demonstrate that FANCJ is important for FANCD2 stability and proper activation of DNA damage responses to replication blocks induced by hydroxyurea.

Highlights

Fanconi Anemia (FA) is a rare, inherited genetic instability disorder that is characterized by developmental abnormalities and skeletal defects, as well as progressive bone marrow failure leading to aplastic anemia typically prior to the patient reaching his or her teens
There is increased evidence suggesting that FANCJ and FANCD2 directly interact with each other and that FANCJ is necessary for proper FANCD2 response to DNA damage
In order to assess the impact of FANCJ status on FANCD2 and its regulatory partner FANCI, FANCJ was transiently downregulated in a broad spectrum of cell lines that are thought to have an intact complement of FA proteins

Summary

Introduction

Fanconi Anemia (FA) is a rare, inherited genetic instability disorder that is characterized by developmental abnormalities and skeletal defects, as well as progressive bone marrow failure leading to aplastic anemia typically prior to the patient reaching his or her teens. There are currently 17 FA complementation groups (FANCA, B, C, D1, D2, E, F, G, I, J, L, M, N, O, P, Q, and S), each representing a functional gene that can be mutated to cause the disorder. These proteins all appear to work in conjunction with the BRCA proteins to preserve genomic stability through the repair of certain types of DNA damage [2, 3]. Following DNA damage the FA core complex, which includes proteins FANCA, B, C, E, F, G, L, and M, is activated and the complex migrates into the nucleus from the cytoplasm [5]. FANCD2 is required for complete activation of DNA replication and damage checkpoints [17], and loss of FANCD2 causes increase in γH2AX levels, indicating the persistence of DNA double strand breaks [17]

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