Fe65 is required for Tip60-directed histone H4 acetylation at DNA strand breaks

Abstract

Fe65 is a binding partner of the Alzheimer's ␤-amyloid precursor protein APP. The possible involvement of this protein in the cellular response to DNA damage was suggested by the observation that Fe65 null mice are more sensitive to genotoxic stress than WT counterpart. Fe65 associated with chromatin under basal conditions and its involvement in DNA damage repair requires this association. A known partner of Fe65 is the histone acetyltransferase Tip60. Considering the crucial role of Tip60 in DNA repair, we explored the hypothesis that the phenotype of Fe65 null cells depended on its interaction with Tip60. We demonstrated that Fe65 knockdown impaired recruitment of Tip60-TRRAP complex to DNA double strand breaks and decreased histone H4 acetylation. Accordingly, the efficiency of DNA repair was decreased upon Fe65 suppression. To explore whether APP has a role in this mechanism, we analyzed a Fe65 mutant unable to bind to APP. This mutant failed to rescue the phenotypes of Fe65 null cells; furthermore, APP/APLP2 suppression results in the impairment of recruitment of Tip60-TRRAP complex to DNA double strand breaks, decreased histone H4 acetylation and repair efficiency. On these bases, we propose that Fe65 and its interaction with APP play an important role in the response to DNA damage by assisting the recruitment of Tip60-TRRAP to DNA damage sites.Alzheimer ͉ APP ͉ DNA repair T he ␤-amyloid peptides, main constituents of senile plaques of Alzheimer disease (AD), derive from the proteolytic processing of a type I membrane protein, known as ␤-amyloid precursor protein (APP) (1). APP functions are not completely understood, and this knowledge could contribute, at least in principle, to the understanding of AD. Possible cues to study the functions of APP could emerge from the analysis of proteins interacting with the short APP cytosolic domain. Several reports indicated that this cytodomain interacts, among the others, with the Fe65 protein (2-4). The latter has the characteristics of an adaptor protein, whose distinctive traits are 3 protein-protein interaction domains, 1 WW and 2 PTB (PhosphoTyrosine Binding) domains (4). The PTB domain located in the C-terminal part of the protein (PTB2) interacts with the cytodomain of APP and of the 2 related proteins APLP1 and APLP2. Similarly, Fe65 has also been found associated with APP intracellular domain (AICD) (5), which is generated, together with the ␤-amyloid peptides, upon the cleavage of APP by secretases (1).Experimental evidence from cultured cells suggested 2 possible functions of Fe65, one depending on its presence in the cytosol and another one on its nuclear localization. APP-Fe65 complexes are present in neuronal growth cones (6) and regulate cell motility (7). Considering that Fe65 WW domain interacts with Mena (8) and APP also with mDab1 (9), these findings support the hypothesis that the APP-Fe65 complex is involved in actin-based membrane remodeling, neurite growth and/or synaptic plasticity. The analysis of the phenotypes of APP/APLP1/APLP2 triple KO ...

Fe65 matters: New light on an old molecule

“…2). Of course, Fe65 suppression leads to reduced phosphorylation of H2AX and decreased efficiency of DNA repair (52). The crucial involvement of APP in this machinery is supported by the observation that APP/APLP2 knockdown has the same effects observed with Fe65 suppression, that is, reduced recruitment of Tip60 at DNA breaks and reduced histone H4 acetylation (52).…”

“…A first set of experiments demonstrated that the Fe65 knockdown hampers the recruitment of Tip60 at DNA strand breaks and in turn the acetylation of histone H4 (52). This event could explain the defects in the DNA damage response and in the DNA repair observed as a consequence of Fe65 suppression.…”

“…Of course, Fe65 suppression leads to reduced phosphorylation of H2AX and decreased efficiency of DNA repair (52). The crucial involvement of APP in this machinery is supported by the observation that APP/APLP2 knockdown has the same effects observed with Fe65 suppression, that is, reduced recruitment of Tip60 at DNA breaks and reduced histone H4 acetylation (52). Considering that AICD seems not to be necessary in this machinery, the most likely explanation for the role of APP in the mechanism is that the interaction of Fe65 with APP is necessary to allow Fe65 to acquire the proper conformation.…”

Regulation of the Physiological Function and Metabolism of AβPP by AβPP Binding Proteins

“…Recent reports also showed that FE65 involved in the response of cell stress, especially to DNA damages [88,96]. FE65 and APP have also been shown to regulate neuronal membrane motility by interacting with Mena, a regulator of actin dynamics that is important for neurite growth and synapse modification [90,91]. The physiological roles of the FE65…”

FE65 regulates and interacts with the Bloom syndrome protein in dynamic nuclear spheres – potential relevance to Alzheimer's disease

“…The present knowledge for FE65 function includes a role for FE65 in DNA repair, especially following DNA double strand breaks (Minopoli et al, 2007;Stante et al, 2009). However, the molecular mechanism is unknown.…”