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#nuclear structure

2 public questions tagged with this topic.

Cell Organelles

The nuclear matrix contains proteins such as:

Nuclear interior contains skeletal framework operationally defined as material insoluble after detergent extraction, DNase digestion and high-salt removal of chromatin. This nuclear matrix comprises lamins A and B at periphery plus internal matrin family proteins Matrin-3, Matrin F, hnRNPs, SAF-A and actin-related proteins that form ten nanometer filaments and fibrogranular networks visible by resinless embedding EM. Matrin-3 is RNA- and DNA-binding protein with zinc-finger domains retaining hyperedited RNAs and anchoring matrix attachment regions to organize loops, mutated in familial amyotrophic lateral sclerosis. Lamin B remains associated throughout extraction, lamin A/C contributes to internal foci. Kinesin and dynein are microtubule motors functioning in cytoplasm, actin and myosin generate contractile forces in cytoplasm not nucleus except for nuclear myosin one, SNARE and COPI mediate vesicle fusion and coating in secretory pathway not nucleus. Matrix organizes replication factories, transcription hubs and splicing speckles, providing structural context for genome function. Integration with cell cycle kinases, calcium signaling and mechanical cues ensures coordinated remodeling during growth, migration and differentiation.

Ref: Berezney Annu Rev Cell Biol; nuclear matrix lamin matrin-3 scaffold MAR organizes transcription factories.

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Cytoskeleton

What is the function of the nuclear lamina?

Interphase nucleus experiences mechanical stresses from cytoskeletal pulling forces migration through constricted spaces and chromatin dynamics requiring reinforcement beyond lipid bilayer envelope alone. Nuclear lamina provides mechanical support as dense meshwork 10 to 20 nm thick apposed to inner nuclear membrane beneath lamina associated chromatin domains. Composed of A type lamins lamin A and C splice isoforms and B type lamins B1 B2 type V intermediate filament proteins forming coiled coil dimers assembling head to tail polymers into orthogonal filaments crosslinked into sheet. Mesh confers elastic stiffness about 2 to 5 fold increasing nuclear rigidity buffers deformation prevents rupture under high strain anchors nuclear pore complexes basket tethers lamina associated domains LADs enriched heterochromatin regulating transcription silencing. Additional functions include mechanotransduction signaling via emerin to regulate gene expression and DNA repair scaffolding through 53BP1. Disassembly mediated by CDK1 phosphorylation disassembles filaments during mitosis enabling nuclear envelope breakdown chromosome capture. Additional regulatory inputs including phosphorylation, small GTPases, and cargo adaptors fine tune filament assembly stability and motor activity matching cellular demands during division, migration, and mechanical stress responses efficiently.

Ref: Dechat et al., Genes Dev 2008 – Nuclear lamina provides mechanical support to nucleus function.

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