RR10

Question 1

What is nucleo-cytoplasmic transport?

Answer 1

Moving mRNA from nucleus to cytoplasm for translation.

Question 2

What is the nuclear pore complex?

Answer 2

• It has inner and outer membrane
• Baskets used for movement of macromolecules in and out of nucleoplasm and cytoplasm
• Smaller molecules freely diffuse through the NPC. Bigger molecules and multi-molecular complexes must be transported.

Question 3

What does transport through the NPC depend on?

Answer 3

It depends on hydrophobic interactions.

Question 4

Why do large molecules need specific transported to be transport through the NPC?

Answer 4

Because there is a gel like substance in the nuclear pore which blocks diffusion and large molecules transporting through.

Question 5

Where are nuclear proteins synthesized and transported?

Answer 5

They are synthesized in the cytoplasm and imported through NPCs/

Question 6

What signal is needed to enter NPC and what signal is needed to leave?

Answer 6

NLS is the nuclear localization signal needed to enter and NES is needed to exit.

Question 7

Describe the GTP/GDP cycle?

Answer 7

GTP is active and then GAP turns it off to inactive and makes it GDP (inactive) and then GEF turns it on and makes GTP which is active.

Question 8

What is RAN?

Answer 8

It is a G protein that exists in GTP bound or GDP bound conformation.

Question 9

What are nuclear transport receptors?

Answer 9

Importins bind to NLS on cargo proteins to facilitate transport through pore by association with FG- nuclear proteins.

Question 10

How do importins work?

Answer 10

Importin interacts with protein that has NLS (signal) and can form a complex that diffuses into nucleus based on concentration gradient (more cargo on cytoplasmic side). Importins facilitate this through its interaction with FG repeats, in the nucleoplasm, greeted by RAN Ran, GEF in GTP bound form (active), removes cargo from and attaches to importin.

Question 11

What is RAN GTP?

Answer 11

Importin that makes its way into cytoplasm based on RAN GTP: importin complex concentration gradient. It is greeted in the cytoplasm by RAn GAP which removes Ran from importin.

Question 12

Where is there high importin concentration?

Answer 12

In the cytoplasm (gradient to get in)

Question 13

Where is there high ran GTP concentration?

Answer 13

In the nucleus, gradient to get out.

Question 14

What is RAN dependent driven by?

Answer 14

It is driven by GDP concentration.

Question 15

What is nuclear export?

Answer 15

When the protein leaves the nucleus.

Question 16

How does nuclear export work?

Answer 16

Exportin + NESCargo + Ran GTP form a complex.
It makes its way out based on the concentration gradient of this trimeric complex. It is greeted in the cytoplasm by RanGAP and removes the cargo into the cytoplasm. Exportin and ran go back into the nucleus.

Question 17

What is the function of exportin t?

Answer 17

It functions to export tRNAs. It binds fully processed tRNs and Ran-GTP, passes through NPCs. The complex dissociates in cytosol when it interacts with Ran-GAP.

Question 18

How are mRNAs exported from the nucleus?

Answer 18

In a Ran independent process using a mRNA exporter.

Question 19

How is mRNP (messenger ribonucleoprotein) transported through the nuclear pore complex?

Answer 19

It is transported in Ran independent manner. It uses NXFI and NXTI which is critical for movement of mature RNAs to export. It binds RNA with mRNP proteins and forms a domain that interacts with FG repeats in nucleoporins.

Question 20

What are Balbiani rings?

Answer 20

They allow for microscopic imaging if mRNP export.