Nuclear Structure and Transport Mechanisms

Nucleus

Largest organelle in animal cells, contains DNA.

Nuclear Membranes

Inner and outer membranes enclosing the nucleus.

Nuclear Pore Complex

Protein structures allowing material transport across membranes.

Nuclear Lamina

Structural network of lamins supporting the nucleus.

Nucleolus

Site for ribosomal RNA production and assembly.

Nucleoplasm

Fluid within the nucleus, contains chromatin.

Heterochromatin

Condensed DNA regions, non-transcribable, near membrane.

Cajal Bodies

Centers for assembly of spliceosomal snRNPs.

Nuclear Speckles

Storage regions for proteins involved in splicing.

PML Bodies

Sites for DNA repair and apoptosis regulation.

Nuclear Transport Receptors

Proteins that escort cargo into the nucleus.

Nuclear-localization Signal (NLS)

Sequence directing proteins to the nucleus.

Importin

Transport receptor binding NLS for nuclear import.

Ran-GTP

Activated form of Ran facilitating protein release.

Exportin

Receptor that transports proteins out of the nucleus.

Nuclear-export Signal (NES)

Leucine-rich sequence for nuclear export of proteins.

NXF1/NXT1

Export receptors for mRNA-protein complexes.

mRNP

Messenger ribonucleotide complex associated with mRNA.

HIV Rev Protein

Regulates export of unspliced viral mRNAs.

Guanine Exchange Factor (GEF)

Activates Ran-GDP to Ran-GTP in nucleus.

GTPase-activating Protein (GAP)

Stimulates Ran-GTP hydrolysis in cytoplasm.

FG-nucleoporins

Proteins forming gel-like matrix in nuclear pores.

Cytoplasmic Filaments

Extend from NPC into cytosol for transport.

Ribonucleoprotein Complexes

Assemblies of RNA and protein in the nucleus.

Transcription Factors

Proteins that regulate gene expression in the nucleus.

Ribosomal Subunits

Components assembled in the nucleolus for protein synthesis.

RNA Helicase (Dbp5)

Removes export factors from mRNA in cytoplasm.

Leucine-rich Region

Sequence motif in NES for nuclear export.