The Fanconi anemia pathway promotes DNA glycosylase‐dependent excision of interstrand DNA crosslinks

Abstract

Fanconi anemia (FA) is a recessive cancer prone syndrome featuring bone marrow failure and hypersensitivity to DNA interstrand crosslinks (ICLs) and, to a milder extension, to ionizing radiation and oxidative stress. Recently, we reported that human oxidative DNA glycosylase, NEIL1 excises with high efficiency the unhooked crosslinked oligomer within three-stranded DNA repair intermediate induced by photoactivated psoralen exposure. Complete reconstitution of repair of the ICL within a three-stranded DNA structure shows that it is processed in the short-patch base excision repair (BER) pathway. To examine whether the DNA damage hypersensitivity in FA cells follows impaired BER activities, we measured DNA glycosylase and AP endonuclease activities in cell-free extracts from wild-type, FA, and FA-corrected cells. We showed that immortalized lymphoid cells of FA complementation Groups A, C, and D and from control cells from normal donors contain similar BER activities. Intriguingly, the cellular level of NEIL1 protein strongly depends on the intact FA pathway suggesting that the hypersensitivity of FA cells to ICLs may, at least in part, arise from downregulation or degradation of NEIL1. Consistent with this result, plasmid-based expression of the FLAG-tagged NEIL1 protein partially complements the hypersensitivity FA cells to the crosslinking agents exposures, suggesting that NEIL1 specifically complements impaired capability of FA cells to repair ICLs and oxidative DNA damage. These findings shed light to how the FA pathway may regulate DNA repair proteins and bring explanation for the long-time disputed problem of the oxidative stress sensitive phenotype of FA cells.

Epigenetic screen of human DNA repair genes identifies aberrant promoter methylation of NEIL1 in head and neck squamous cell carcinoma

“…32 Furthermore, NEIL1 has been shown to interact with other DNA repair genes which have been linked to cancer. 31,33,34 The level of NEIL1 is greatly diminished in cells depleted for FANC proteins and Fanconi anemia cell lines. Expression of the NEIL1 protein partially reverses the hypersensitivity of Fanconi anemia cells to interstrand crosslinks.…”

“…Expression of the NEIL1 protein partially reverses the hypersensitivity of Fanconi anemia cells to interstrand crosslinks. 34 However, very few data on a possible epigenetic regulation of this gene are so far available. We show here for the first time that NEIL1 is consistently hypermethylated in HNSCC tissues and HNSCC cell lines.…”

Base excision repair: A critical player in many games

“…In the past several years there has been evidence that BER may play a role in interstrand crosslink repair (for reviews see [80,97,98]). Interstrand crosslinks can be formed endogenously by malondialdehyde, a product of lipid peroxidation, as well as by exogenous agents, and can be repaired by NER or homology-directed repair (HDR).…”

DNA Interstrand Cross-Linking Agents and their Chemotherapeutic Potential

“…The repair mechanism has been frequently reviewed because of rapid advances in this sector or authors attempt to provide details of some particular step or bring a different point of view on this process. The most recent reviews are focused specifically on a description of a role of proteins involved in the repairing [65][66][67][68][69], selected processes involved in the mechanism [70][71][72], repair of DNA during S phase of the cell cycle [73], initiation of ICL repair process [74], repairing in context of finding new targets in chemotherapy [75][76][77] or overall summary of repairing [61,[78][79][80]. In the following part we briefly summarize the current state of knowledge to demonstrate the difficulty and complexity of the ICL repairing in the context of actual possibilities for chemotherapeutic treatment.…”