Lecture 2

Question 1

What makes up nuclear compartmentation?

Answer 1

nucleoplasm (nuclear subdomains), nuclear matrix, nuclear envelope, and nuclear lamina

Question 2

What two functions are the nucleus responsible for?

Answer 2

1. Compartmentalization of the cellular genome and its activities
   (e.g., site of DNA replication, transcription & RNA processing)
   e.g., site where translation components (ribosomes, mRNAs, tRNAs) are synthesized
2. Coordination of cellular activities
   e.g., control of metabolism, protein synthesis, reproduction (cell division), etc.

Question 3

What is the nucleoplasm?

Answer 3

• fluid-filled interior of nucleus – highly organized
• consists of >30 specialized regions (‘subdomains’) that participate in specific functions (Note: nuclear subdomains are not membrane bound)

Question 4

What are interchromosomal channels?

Answer 4

regions between chromosome subdomains that serve as barriers to prevent unwanted DNA-DNA and/or DNA-protein interactions

Question 5

What is a nuclear matrix and what are the three major filament systems which are composed of it?

Answer 5

Nuclear matrix is an insoluble fibrillar-like protein network (‘mesh’) distributed throughout nucleoplasm

• analogous to cytokeleton network in cytoplasm
  composed of 3 major filament systems: microtubules, actin microfilaments & intermediate filaments

Question 6

What are the three main parts which compose the nuclear envelope?

Answer 6

*Nuclear membrane
*nuclear lamina
*nuclear poor complexes

Question 7

what is the nuclear poor complex responsible for?

Answer 7

NPC is responsible for regulating trafficking (import & export) of all substances between nucleus and cytoplasm

Question 8

What is the nuclear poor complex composed of?

Answer 8

composed ~40 different proteins - nucleoporins (‘Nups’)

Question 9

What are the several parts consisting in the nuclear pore complex?

Answer 9

Nuclear pore complex consists of several parts:
* central scaffold – composed of integral/trans membrane-bound nucleoporins, anchors NPC to nuclear envelope membranes (at junction of outer and inner membranes)
* This forms of central channel - inner surface of channel lined by ‘filament-like’ Nups - FG nucleoporins
* FG nucleoporins possess highly disordered 2o structure and an unusual amino acid composition, hydrophilic polypeptides with short repeats of hydrophobic domains enriched in phenylalanines and glycines (‘FG domains’)
* Y-complexes including cytoplasmic ring and nuclear ring both composed of structural Nups, located on cytoplasmic and nucleoplasmic side of NPC
* cytoplasmic filaments - long, filament-shaped (structural) Nups that extend into cytoplasm, involved in nuclear receptor-cargo protein recognition and import from cytoplasm
* nuclear basket, basket, like structure located on the nuclear side of NPC linked to Y complex nuclear rank