The role of prelamin A post-translational maturation in stress response and 53BP1 recruitment

Abstract

Lamin A is a main constituent of the nuclear lamina and contributes to nuclear shaping, mechano-signaling transduction and gene regulation, thus affecting major cellular processes such as cell cycle progression and entry into senescence, cellular differentiation and stress response. The role of lamin A in stress response is particularly intriguing, yet not fully elucidated, and involves prelamin A post-translational processing. Here, we propose prelamin A as the tool that allows lamin A plasticity during oxidative stress response and permits timely 53BP1 recruitment to DNA damage foci. We show that while PCNA ubiquitination, p21 decrease and H2AX phosphorylation occur soon after stress induction in the absence of prelamin A, accumulation of non-farnesylated prelamin A follows and triggers recruitment of 53BP1 to lamin A/C complexes. Then, the following prelamin A processing steps causing transient accumulation of farnesylated prelamin A and maturation to lamin A reduce lamin A affinity for 53BP1 and favor its release and localization to DNA damage sites. Consistent with these observations, accumulation of prelamin A forms in cells under basal conditions impairs histone H2AX phosphorylation, PCNA ubiquitination and p21 degradation, thus affecting the early stages of stress response. As a whole, our results are consistent with a physiological function of prelamin A modulation during stress response aimed at timely recruitment/release of 53BP1 and other molecules required for DNA damage repair. In this context, it becomes more obvious how farnesylated prelamin A accumulation to toxic levels alters timing of DNA damage signaling and 53BP1 recruitment, thus contributing to cellular senescence and accelerated organismal aging as observed in progeroid laminopathies.

Mineralocorticoid Receptor Antagonism Prevents Type 2 Familial Partial Lipodystrophy Brown Adipocyte Dysfunction

“…Our study also shows that drugs inducing non-farnesylated and mostly farnesylated prelamin A trigger MR recruitment to the nuclear envelope, suggesting that prelamin A has a higher affinity for MR relative to mature lamin A. However, given the stronger effect of farnesylated prelamin A, we can speculate that inhibition of prelamin A farnesylation by statins or lonafarnib [33] might restore a more physiological condition in FPLD2 brown adipocytes and other LMNA-linked lipodystrophies featuring farnesylated prelamin A accumulation, such as Mandibuloacral Dysplasia and Hutchinson-Gilford Progeria [52]. Of note, MR is a trigger of IL6 expression, a main determinant of LMNA-linked lipodystrophy [17,53].…”

“…Cell transfection. HEK293 cells were transfected with MR-GFP alone or in combination with FLAG-tagged plasmids containing wild-type prelamin A (LA-WT), which undergoes normal maturation, and prelamin A carrying the pathogenetic variant R482Q causing FPLD2 (LA-R482Q), unprocessable prelamin A (LA-C661M, non-farnesylated prelamin A), or uncleavable prelamin A (LA-L647R, farnesylated prelamin A) [33]. Transfections were performed using Fugene transfection reagent (Invitrogen, Thermo Fisher Scientific) according to the manufacturer's instructions.…”

“…Nevertheless, inhibition of MR dimerization by spironolactone almost completely abolished the lamin A-MR interaction (Figure 4b). As prelamin A tends to accumulate in FPLD2 cells [10,11,31,35], we analyzed MR fate in the presence of LA-C661M encoding the full-length unprocessable prelamin A, which is accumulated in the nuclear lamina as non-farnesylated prelamin A, or LA-L647R, which encodes an uncleavable permanently farnesylated prelamin A form [33]. Both prelamin A forms are accumulated in FPLD2 and other LMNA-linked lipodystrophies [36][37][38][39].…”

Role of C-Terminal Phosphorylation of Lamin A in DNA Damage and Cellular Senescence

“…The C-terminal of prelamin A post-translational maturation is involved in the DNA damage response. Aberrant accumulation of prelamin A at the early stages of the stress response reduces H2AX phosphorylation and 53BP1 recruitment/release, thus contributing to cellular senescence and accelerated organismal aging in progeroid laminopathies [28]. Our previous studies found that heterochromatic structure is closely related to the DNA damage repair pathway in cells undergoing premature aging [29].…”