Nonerythroid αII spectrin is required for recruitment of FANCA and XPF to nuclear foci induced by DNA interstrand cross-links

Abstract

The events responsible for repair of DNA interstrand cross-links in mammalian cells, the proteins involved and their interactions with each other are poorly understood. The present study demonstrates that the structural protein nonerythroid α spectrin (αSpIIΣ*), present in normal human cell nuclei, plays an important role in repair of DNA interstrand cross-links. These results show that αSpIIΣ* relocalizes to nuclear foci after damage of normal human cells with the DNA interstrand cross-linking agent 8-methoxypsoralen plus ultraviolet A (UVA) light and that FANCA and the known DNA repair protein XPF localize to the same nuclear foci. That αSpIIΣ* is essential for this re-localization is demonstrated by the finding that in cells from patients with Fanconi anemia complementation group A (FA-A), which have decreased ability to repair DNA interstrand cross-links and decreased levels of αSpIIΣ*, there is a significant reduction in formation of damage-induced XPF as well asαSpIIΣ* nuclear foci, even though levels of XPF are normal in these cells. In corrected FA-A cells, in which levels of αSpIIΣ*are restored to normal, numbers of damage-induced nuclear foci are also returned to normal. Co-immunoprecipitation studies show thatαSpIIΣ*, FANCA and XPF co-immunoprecipitate with each other from normal human nuclear proteins. These results demonstrate thatαSpIIΣ*, FANCA and XPF interact with each other in the nucleus and indicate that there is a close functional relationship between these proteins. These studies suggest that an important role for αSpIIΣ* in the nucleus is to act as a scaffold, aiding in recruitment and alignment of repair proteins at sites of damage.

The Fanconi Anemia/BRCA pathway: new faces in the crowd

“…Accordingly, disruption of the FA pathway results in persistence of DNA breakage (Rothfuss and Grompe 2004). It is interesting to note that although XPF/ERCC1 has been reported to colocalize with FANCA, suggesting it may function in the FA pathway (Sridharan et al 2003), XPF/ERCC1 mutant cells demonstrate normal FANCD2 monoubiquitination (R.D. Kennedy and A.D. D'Andrea, unpubl.).…”

Brain proteins interacting with the tetramerization region of non-erythroid alpha spectrin

“…Alpha spectrin is identified at the nuclear envelope [30]. More recently, Lambert and colleagues demonstrated that SpαII is involved in DNA repair in the nucleus [19,20,48,49] (Tab. 2).…”

“…Indeed, SpαII was described as a component of a chromatin-associated complex that was involved in the repair of DNA inter-strand crosslinks, and was identified as being a direct binding partner of the DNA-repair proteins, FANCA and FANCC [48]. Subsequent studies have shown that SpαII binds directly to DNA inter-strand cross-links [18,49]. SpαII is localized to multiple nuclear foci along with two DNA-repair proteins (FANCA and XPF) to which it binds directly [49].…”

Other Proteins Interacting with XP Proteins

“…73,74 Furthermore, XPF interacts with the FANC-A, Msh2, and non-erythroid α Spectrin αSPIIΣ proteins, further demonstrating its role in the removal of interstrand crosslinks. [75][76][77][78] A recently identified interesting role for XPF is its interaction with the telomere elongation factor TRF2. This factor is responsible for the conversion of telomeric TTAGGG repeats tracts to T-loop structures that protect the telomeres from inadvertent double-strand break repair.…”