Week 9 - Nucleus Flashcards
What 5 things are inside the nucleus
Histone
Nucleosome
Chromatin
Chromosome
Sister chromatids
Describe the nucleus
Largest single organelle, containing all genetic material packaged as chromatin
Site of RNA synthesis and contains nucleolus
Describe the nuclear pore complex
Large protein structure, an aqueous channel connecting nucleoplasm to cytosol
Molecule sizes and how it relates to transport through nuclear pore complex
<5KDa freely diffuses
>5 - <60KDa takes longer but diffuses
>60KDa requires mechanism and energy
What is the role of nuclear localisation signals
Tell a protein to go into the nucleus
Proteins synthesised on a cytosilic ribosome containing a NLS
What are NLS recognised by
Nuclear Import receptors
How do NIRs work
They bind to FG repeats on nucleoporins in the cytosolic domain of the NPC
What is GTP
Guanosine triphosphate
What is a GTP binding protein
Protein that binds to GTP and acts as GTPase (GTP->GDP)
What is GAP
GTPase activating protein. Binds to GTP binding protein and induces GTP hydrolysis
What is GEF
Guanine nucleotide exchange factor, binds to GTP binding protein and causes release of GDP
Describe nuclear import
NIR binds to protein which has nuclear localisation signal, enters nucleus and Ran-GTP takes place of protein, releasing the protein from the NIR, then after leaving nucleus Ran-GDP dissociates from NIR and cycle can repeat
Describe nuclear export
NER enters nucleus, binds to Ran-GTP which allows protein with nuclear export signal to bind to NER, protein leaves and Ran-GDP dissociates and protein leaves into cytosol leaving NER to repeat cycle
What are the two forms of chromatin in the nucleolus
Heterochromatin and euchromatin
What is heterochromatin
Transcriptionally inactive and densely packed chromatin
