Progerin's Hyperstability Physically Disrupts SETD2-CDK1 Scaffolding, Amplifying Genomic Instability Beyond Physiological Aging

The nuclear lamina's role as a signaling scaffold is well-established, but how specific laminopathies differentially corrupt this function remains unclear. Progerin, the mutant lamin A in Hutchinson-Gilford progeria syndrome (HGPS), forms hyperstable filaments due to retained farnesylation, resisting mitotic depolymerization (Progerin resists mitotic depolymerization via hyperstable filaments from retained farnesyl). This contrasts with physiological aging, where declining ZMPSTE24 activity causes prelamin A accumulation without progerin's splice defect, leading to subtler lamina dysfunction (physiological aging features ZMPSTE24 activity decline leading to prelamin A accumulation without progerin's splice defect). A key mechanistic gap is how progerin's structural rigidity impacts active signaling pathways, particularly the SETD2-CDK1 axis.

SETD2 scaffolds CDK1 to phosphorylate lamin A/C at S22 and S392, enabling mitotic lamina disassembly (SETD2 scaffolds CDK1 to phosphorylate lamin A/C S22/S392 for depolymerization, and SETD2 loss causes lamina invaginations and genomic instability). Disruption of this axis causes lamina invaginations, micronuclei, and DNA damage. In HGPS, progerin's hyperstable filaments may not only resist depolymerization but also physically sequester or mislocalize SETD2, impairing its scaffolding function. This could create a feedforward loop: reduced CDK1 access to lamin substrates exacerbates lamina persistence during mitosis, compounding genomic instability through increased R-loops and transcription-replication conflicts (LMNA depletion directly drives R-loop accumulation, transcription-replication conflicts, and DNA damage).

In contrast, prelamin A accumulation in aging may allow more dynamic SETD2-CDK1 interactions due to less rigid filament structures, resulting in milder signaling deficits. This hypothesis is supported by evidence that nuclear pore complexes and lamina proteins actively regulate genes, with age-related changes disrupting lamina-chromatin contacts (nuclear pore complexes are active gene regulators, and age-related changes may disrupt lamina-chromatin contacts). Progerin's dominance might extend to interfering with NPC-lamina crosstalk, potentially linking to caspase-mediated NPC trimming in aging.

Testable predictions:

1. Progerin-expressing cells will show reduced proximity between SETD2 and CDK1 at the lamina compared to cells with prelamin A accumulation, measurable by proximity ligation assays.
2. Phosphorylation levels at lamin A/C S22/S392 will be lower in progerin contexts during mitosis, correlating with increased micronuclei formation.
3. SETD2 overexpression or CDK1 activation should partially rescue lamina disassembly defects in progerin cells but not in prelamin A cells, highlighting differential mechanisms.

This hypothesis challenges the view of progerin as merely a structural impediment; it proposes an active hijacking of signaling scaffolds. If validated, it could inform targeted therapies for progeria that focus on restoring SETD2-CDK1 dynamics rather than solely stabilizing lamina integrity.