Exam 3- Nuclear Organization and Nuclear Compartments

Question 1

How are chromosomes distributed within the nucleus?

Answer 1

Chromatin

Question 2

What 4 nuclear domains?

Answer 2

Replication factories

Nuclear Speckles

Pro-Myelocytic Leukemia Nuclear Bodies (PML-NBs)

Nucleoli / Nucleolus

Question 3

What are replication factories?

Answer 3

Domain that houses all the proteins needed for DNA replication

Question 4

What are nuclear speckles?

Answer 4

Storage site for splicing machinery.
In actively dividing cells and highly transcribed genes.
This enhances efficiency

Question 5

What are Pro-Myelocytic Leukemia Nuclear Bodies (PML-NBs)?

Answer 5

plays a role in storing transcription factors and chromatin remodeling factors.
Most of these proteins are sumoylated (match maker for proteins).

Fixed by trans-retanoic acid

Question 6

What is the nucleolus?

Answer 6

Only nuclear domain that can be seen with a light microscope WITHOUT dye

This is the site of rRNA processing, ribosomal assembly

Must reform after cell division

Inside nucleolar organization regions

Question 7

What happens to the nucleus during mitosis?

Answer 7

It disappears. The structural components are disassembled but are rapidly re-assembled at the end of mitosis.

Question 8

What’s the critical event that triggers nuclear disassembly during mitosis?
What’s the post-translational modification that regulates it?

Answer 8

Phosphorylation of the lamin proteins to disrupt the inner nuclear membrane.

Question 9

How is the nucleus reassembled after mitosis?

What are the key molecular interactions that drive its reassembly?

Answer 9

as you move through mitosis and the cell divides, the chromosomes associate with the NE-Lamin vesicles that formed across the cytoplasm- because lamins can bind DNA.
As the vesicles surround the DNA, they all fuse together (vesicle fusion) to create a large membrane around the chromosomes.
Later all the vesicles with DNA fuse to remake the nucleus.
Lamins must be dephosphorylated.