Lamin proteins form an internal nucleoskeleton as well as a peripheral lamina in human cells

TLDR

The nuclear lamina is a protein mesh beneath the nuclear membrane composed of lamins A, B, and C, which are traditionally thought to reside only at the nuclear periphery. Internal lamins are embedded in dense chromatin and become detectable by antibody labeling only after chromatin removal, allowing visualization of internal skeleton knobs and nodes with fluorescein‑ or gold‑conjugated anti‑lamin A antibodies. The study demonstrates that lamins form a diffuse internal nucleoskeleton, indicating that the term “lamin” is misleading because they are not confined to the nuclear periphery.

Abstract

ABSTRACT The nuclear lamina forms a protein mesh that underlies the nuclear membrane. In most mammalian cells it contains the intermediate filament proteins, lamins A, B and C. As their name indicates, lamins are generally thought to be confined to the nuclear periphery. We now show that they also form part of a diffuse skeleton that ramifies throughout the interior of the nucleus. Unlike their peripheral counterparts, these internal lamins are buried in dense chromatin and so are inaccessible to antibodies, but accessibility can be increased by removing chromatin. Knobs and nodes on an internal skeleton can then be immunola-belled using fluorescein- or gold-conjugated anti-lamin A antibodies. These results suggest that the lamins are misnamed as they are also found internally.