Lec 9

Question 1

Eukaryotic cells mostly have a

Answer 1

Circular nucleus

Question 2

RBCs have no

Answer 2

Nucleus

Question 3

Nuclear pores

Answer 3

Many pores exist and are very large

Question 4

What enters the nucleus

Answer 4

Nucleotides

RNA Pols
Spliceosomes
Transcription factors
DNA Pols
Histones
Cdk/Cyclin proteins

Question 5

What leaves the nucleus

Answer 5

mRNAs
tRNAs

Ribosomes

Question 6

Nucleotides

Answer 6

Needed for RNA synthesis, DNA replication and DNA repair

Question 7

Hypothesis for nucleotide movement

Answer 7

They are small enough to enter by diffusion

Question 8

Experiment for nucleotide movement

Answer 8

Inject gold balls into cytosol of cell

Wait

See if the cells have entered using ultrathin sectioning + stain + TEM

Question 9

Result of nucleotide movement

Answer 9

Diffusion is possible

Question 10

Test of discovery

Answer 10

Observing a process

Question 11

Test of necessity experiment

Answer 11

Removing something from a process and seeing if it still occurs

Question 12

Test of sufficiency experiment

Answer 12

If you add something does a new process occur

Question 13

NLS
nuclear localization signal

Answer 13

All proteins have an NLS

Question 14

NLS discovery

Answer 14

Virus protein infects a cell and causes the host to burst with more virus cells

Question 15

T-antigen amino acids 126-132 is

Answer 15

Necessary for nuclear localization

Question 16

E coli experiment

Answer 16

Adding B-GAL to the T-antigen is sufficient for nuclear localization

Question 17

Test of necessity is

Answer 17

Easier and should be done before test of sufficiency is possible

If you find something is not necessary there is no reason to do a sufficiency experiment

Question 18

What is requires for nuclear import

Answer 18

An NLS (marks protein for being destined for the nucleus)

Importin (Import protein)

Question 19

Importin

Answer 19

Binds to anything with an NLS and binds to nuclear pore to deliver cell. It lets go of cell once the import is done

Question 20

Nuclear export needs

Answer 20

Needs NES (Nuclear Export Signal)

Exportin

Question 21

Exportin

Answer 21

Associates with NES or RNA directly and nuclear pore

Same as importin mechanism but backwards

Question 22

What drives transport in the right direction

Answer 22

Importins and exportins has a high affinity for the nuclear pore

Importins have a high affinity for the cargo in the cytosol but a low one in the nucleus, which is why they let go in the nucleus

The opposite is true for exportins

Question 23

Ran

Answer 23

Ran-GTP is the active form

Ran-GDP is the inactive form

Ran-GTP has a high affinity for importins and exportins

Ran-GDP is in the cytosol and Ran-GTP is in the nucleus

When active Ran binds to the importin in the nucleus, importin lets go of its cargo and exits the nucleus along with Ram

When Ran binds to an exportin, it also binds to the cargo and leaves the cell, where it Ran becomes inactive and lets go of the exportin, exportin then lets go of its cargo and goes back to the nucleus alone

Question 24

Affinity for the nucleus is due to

Answer 24

Ran