Key Words Lectures 2-5 Flashcards
1
Q
Cellular Compartmentalization
A
allows for larger size and segregation and organization of specific cellular functions
2
Q
Nucleus
A
2 main functions:
1. ** Compartmentalization of the cellular genome and its activities **(ie: site of DNA rep. and site where translation cmponents are synthesized
2. Coordination of cellular activities (ie: metabolism, protein synthesis, cell division etc.)
3
Q
Nucleoid
A
- only in prokaryotes
- region where chromosome is located
- less DNA and DNA packaging and limited/no RNA processing
4
Q
Nucleolus
A
- most conspicuous nuclear subdomain (irregular shaped, dense and granular)
- size and number depend on metabolic activity of cell
- function in producing ribosomes (rDNA transcription, rRNA processing, initial stages of ribosomal subunit)
5
Q
Nucleoplasm
q
A
- fluid-filled interior of nucleus
- has >30 specialized subdomains that participate in specific functions (nuclear subomains are not membrane bound)
6
Q
Transcription Factories
A
- formed by active genes of different subdomains that extend into interchromosomal channels
- where transcription factors are concentrated
7
Q
Interchromosomal channels
A
- regions between chromosome subdomains
- serve as barriers to prevent unwanted DNA-DNA and/or DNA-protein interactions
8
Q
Nuclear speckles
A
- subdomains of nucleus where mRNA splicing factors are concentrated (where pre-mRNA processing occurs)
- often located in interchromosomal channels next to transcription factories
- numerous and highly dynamic
9
Q
Nuclear Matrix
A
- insoluble fibrillar-like protein network distributed throughout nucleoplasm
- structural role - maintains overall shape of nucleus
- serves as a scaffold - responsible for organizing nuclear subdomains and anchoring protein factors
10
Q
Nuclear Envelope
A
- seperates contents of nucleus (ie: genome) from surrounding cytoplasm
- serves as a barrier which requires regulated passage of molecules between nucleus and cytoplasm
- establishes unique composition of nucleus and spatially regulates gene expression
- provides structural framework for nucleus
- 3 main parts (nuclear membranes, nuclear lamina, nuclear pore complexes)
11
Q
Inner Nuclear Membrane
A
- has a unique protein composition
- joined to outer nuclear membrane at nuclear pore complexes
- phospholipid bilayer
- serves as a barrier to passage of ions, solutes, macromolecules between nucleus and cytoplasm
12
Q
Outer Nuclear Membrane
A
- continuous with rough endoplasmic reticulum
- ribosomes attached to cytoplasmic surface
- joined to inner nuclear membrane at nuclear pore complexes
- phospholipid bilayer
- serve as barrier to passage of ions, solutes, macromolecules between nucleus and cytoplasm
13
Q
Nuclear envelope lumen
A
- continuous with ER lumen
- seperates inner and outer nuclear membranes
14
Q
Nuclear Lamina
A
- on inner surface (nucleoplasmic side) of nuclear inner membrane
- network of long, filament-like proteins
- provides mechanical support to nuclear envelope
- serves as scaffold fpr attachment of chromatin and nuclear matrix to nuclear envelope
- mutations in these genes are responsible for several human diseases (ie: Hutchinson-Gilford Progeria)
15
Q
ABC Nuclear Lamins
A
- evolutionarily related to proteins that form intermediate filaments in cytoskeleton network
16
Q
Nuclear Pore Complex
A
- channels in nuclear envelope
- regulated trafficking of all substances between nucleus and cytoplasm
- 3000-4000/nucleus ; number is related to nuclear activity
- 8-fold symmetrical structure organized around large, central aqueous channel
17
Q
Nucleoporin
A
- compose the nuclear pore complex
- include intergral and peripheral inner and outer nuclear membrane proteins
- several are related to COPII proteins
- highly conserved among all eukaryotes
18
Q
FG nucleoporins
A
- line the inner surface of the aqueous central channel and limit the diffusion of macromolecules larger than 40kDa (molecules larger cannot pass through the NPC freely)
- hydrophilic polypeptides with short repeats of hydrophobic domains enriched in phenylalanines and glycines
- highly disordered secondary structure
19
Q
Structural Nucleoporins
A
- composes Y-complexes
- composes the nuclear basket
- important for formation of NPC scaffold
20
Q
Central Scaffold
A
- composed of integral/trans membrane-bound nucleoporins
- anchors NPC to nuclear envelope membranes (at junction of inner and outer membranes)
- forms aqueous central channel
- inner surface lined by FG nups
21
Q
Central Channel
A
- site of trafficking between nucleus and nucleoplasm
21
Q
Cytoplasmic Filaments
A
- long, filament-shaped structural nups that extend into cytoplasm
- involved in nuclear receptor-cargo protein recognition and import from cytoplasm
21
Q
Y-complex
A
- includes cytoplasmic ring and nuclear ring
- on cytoplasmic and nuclear side of NPC
- linked to central scaffold and cytoplasmic filaments or nuclear basket
22
Q
Nuclear Localization Signal
A
- amino acid sequence that is both necessary and sufficient for cytoplasm-to-nuclear targeting (necessary - if seq. is mutated, protein doesn’t go to nucleus / sufficient - if seq. linked to non-nuclear protein, still redirects to nucleus)
- specific sequence of amino acids recognized by nuclear receptor proteins
- mediates targeting of protein from cytoplasm to nucleus
22
Nuclear Basket
* basket-like structure made of structural nups on the nucelar side of NPC
* linked to Y-complex nuclear ring
* involved in nucelar receptor-cargo protein import and export to cytoplasm
23
Classic Nuclear Localization Signal
* most common NLS
* short stretch of positively-charged, basic amino acid residues (ie: -KKQRKK)
24
Bipartite Nuclear Localization Sequence
* two short stretches of basic amino acids and 7-10 amino acid long spacer sequence (ie: KR[PAATKAGQA]KKKK)
25
Karyoferin
family of receptor proteins responsible for moving macromolecules into or out of nucleus
26
Importin
* type of karyoferin
* brings macromolecules **into** nucleus
27
Exportin
* type of karyoferin
* bring macromolecules **out of** nucleus
28
importin a
* subunit of importin
* recognizes and binds to basic residues in 'cargo' protein's NLS
29
Importin B
* subunit of importin
* binds to cytoplasmic filament at NPC
30
Ran-GTP
* active form
* concentration higher in the nucleus and lower in the cytoplasm
31
Ran-GDP
* inactive form
* concentration higher in cytoplasm and lower in the nucleus
32
GEF
* Nuclear protein that promotes conversion of Ran-GDP to Ran-GTP
* maintains high Ran-GTP in nucleus (promotes GTPase activity of Ran)
33
GAP
* cytoplasmic protein that promotes hydrolysis of Ran-GTP to Ran-GDP
* maintains low Ran-GDP in cytoplasm
34
Nuclear Export Signal
* nuclear-to-cytoplasm targeting
* necessary and sufficient for this type of targeting
* most common NES consists of leucine-rich motif (-LxxLxxL-)
35
Piggyback nuclear protein import
* proteins imported into nucleus without NLS
* protein lacking NLS bunds to NLS-containing protein in cytoplasm
* targeting and import of protein-protein complex into nucleus mediated by importin
36
Cyclin
* nucleocytoplasmic proteins involved in cell cycle control through checkpoints
* synthesized and degraded during each cell cycle
* bind Cdks and regulate their activity during specific stages of the cell cycle
* low in early interphase (G1)
* high at end of G2/start of M phase
* shuttle between nucleus and cytoplasm
37
Cyclin-Dependent Kinases
* cell-cycle-specific kinase enzymes located in nucleus
* phosphorylate various 'target' nuclear proteins (turn them on and off)
* low in early interphase (G1)
* high in G2/start of M
38
Open Mitosis
* higher eukaryotes
* nucleus completely disassembles by metaphase
* two daughter nuclei reassemble during end of mitosis
39
Closed Mitosis
* lower eukaryotes
* nucleus remains intact during mitosis
39
Proteasome
* degrades pre-existing cyclin proteins after start of M phase
