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#cell nucleus

6 public questions tagged with this topic.

Cell Organelles

The primary function of the nucleolus is:

Electron microscopy reveals nucleolus as darkly staining subnuclear domain due to high RNA protein density, tripartite with fibrillar centers containing inactive rDNA, dense fibrillar component where transcription and early processing occurs, granular component assembling pre-ribosomes. RNA polymerase I with transcription factor UBF drives high-rate synthesis of forty seven S precursor containing eighteen S, five point eight S, twenty eight S RNAs flanked by five prime external transcribed spacer and internal transcribed spacers ITS1 and ITS2. Early cleavages by U3 snoRNP at five prime ETS occ

Ref: Scheer Annu Rev Cell Biol; nucleolus FC DFC GC rRNA transcription processing assembly.

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Cell Organelles

The nuclear lamina is composed of:

Meshwork underlying inner nuclear membrane known as nuclear lamina provides mechanical strength preventing envelope rupture under cytoskeletal tension transmitted via LINC complex and organizes chromatin positioning. It consists of intermediate filament proteins lamins subclassified into B-type encoded by LMNB1 and LMNB2 constitutively farnesylated for membrane anchorage, and A-type encoded by LMNA via alternative splicing producing lamin A including farnesylated precursor processed to mature form and lamin C lacking farnesylation, expressed after differentiation. Lamins assemble via parallel

Ref: Burke Annu Rev Cell Dev Biol; lamins A/B/C type V IF, farnesylation, lattice under inner membrane.

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Cell Organelles

Which nuclear domain is associated with transcriptionally inactive chromatin?

Mammalian nucleus partitions chromatin into active and inactive states with distinct cytology and epigenetic marks. Euchromatin appears lightly stained, decondensed, nuclease hypersensitive and enriched in histone acetylation, H3K4 trimethylation, H3K36 methylation associated with ongoing transcription and replication early S phase, located interiorly. Heterochromatin appears electron dense, concentrates at periphery adjacent to nuclear lamina, around nucleolus and at centromeres, enriched in H3K9 trimethylation, H4K20 trimethylation, HP1 binding and DNA methylation repressing transcription by

Ref: Grewal Annu Rev Genet; heterochromatin H3K9me3 HP1 transcriptionally silent peripheral, euchromatin active.

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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 amyotro

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 conf

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

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