Cell Nucleus Flashcards
What are the nuclear number of proteins and RBCs?
Muscle cells have dozens
RBCs have none
What is the function of the nucleus?
Contains the nuclear genome
Protects DNA
Organizes replication, transcription and RNA processing (regulates genes expression)
What does the nucleus protect DNA from?
Harsh cytosolic environment
Why is the nucleus compartmentalized?
Separate nuclear and cytosolic enzymes
Protect DNA
Separate ribosomes from pre-mRNA to prevent translation
Regulate gene transcription, cell cycle, cytosolic metabolism by shutting factors in and out of nucleus
What does importin bind to?
The NLS (nuclear localization signal) DNA nucleoporins
What does exporting (export receptors in nucleus) bind?
NES and nucleoporins for export
When are G proteins switched “off”?
When bound to GDP (protein GAP hydrolyse GTP)
When are the G protein turned “on”?
By binding GTP (GEF exchange GDP for GTP)
What is the on switch for G proteins?
GEF (guanidine nucleotide exchange factor, On Switch)
Where are GEF and GAP located?
GAP: in cytoplasm (Ran GDP)
GEF: in nucleus (Ran GTP)
What is the anchorage site for chromosomes?
The nuclear lamina
Note: attach chromatin to inner membrane and act as transcription regulators but binding TFs
What does emerin bind to?
To the lamins in the inner membrane
Note: also binds other inner membrane proteins
What lamins for heterodimers?
Lamin A and C
What does lamin phosphorylation during prophase 1 by Cdk1 cause?
Nuclear lamina disassembly
Nuclear envelope disassembly into vesicles containing lamin B
Lamin A and C are released as free dimers
Lamin B is anchored to inner leaflet
How is Cdk1 inactivated?
Lamin dephosphorylation
Note: membrane vesicles bind chromosome surface for reassembly
