The nucleus is a highly organized organelle

• old = bowl of spaghetti
• enhancers and promoters are broght together

nucleus can respond to stimuli

• nuclear speckles
• PML body

nuclear envelope

• outer membrane = continuous with ER, studded with ribosomes
• Inner membrane = heterochromatin (C)
• nuclear pores regulate what comes in and out of cells

nuclear lamina

• mesh work underlying nuclear envelope
• composed of lamin proteins (A, B (fibroblast), C types)
  • assessed into lattice
• give the nucleus its structure

nuclear pores

• 3-4 thousands of pores per nucleus
• donut structure (octagonal symmetry)
• larger things need to be actively transported into the nucleus

nuclear pore complex regulates gene expression

• pores bring in TFs and other modifiers
• cancer can occur from nuclear pore complex forming complex with other TFs
• NUP = nuclear porins

Active chromatin is associated with interior inactive chromatin is located at the envelope

nucleolus

• not membrane bound

• site of rDNA, rRNA gene clustering

• site of ribosome assembly

• transcription factories are distinct regions that have transcription occurring

Phase separation

• membrane-less compartments
• like balsamic vinegar in oil
• Rapidly changeable

Most proteins are synthesized in the cytoplasm

• need to be moved back into the nucleus
• Nuclear localization sequence (NLS)
  • Amino acid sequence (Lys dense)
  • necessary for nuclear import