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MCB2050 > Key Words Lectures 2-5 > Flashcards

Key Words Lectures 2-5 Flashcards

1
Q

Cellular Compartmentalization

A

allows for larger size and segregation and organization of specific cellular functions

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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.)

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3
Q

Nucleoid

A
  • only in prokaryotes
  • region where chromosome is located
  • less DNA and DNA packaging and limited/no RNA processing
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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)
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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)
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6
Q

Transcription Factories

A
  • formed by active genes of different subdomains that extend into interchromosomal channels
  • where transcription factors are concentrated
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7
Q

Interchromosomal channels

A
  • regions between chromosome subdomains
  • serve as barriers to prevent unwanted DNA-DNA and/or DNA-protein interactions
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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
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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
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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)
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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
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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
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13
Q

Nuclear envelope lumen

A
  • continuous with ER lumen
  • seperates inner and outer nuclear membranes
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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)
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15
Q

ABC Nuclear Lamins

A
  • evolutionarily related to proteins that form intermediate filaments in cytoskeleton network
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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
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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
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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
Q

Nuclear Basket

A
  • 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
Q

Classic Nuclear Localization Signal

A
  • most common NLS
  • short stretch of positively-charged, basic amino acid residues (ie: -KKQRKK)
24
Q

Bipartite Nuclear Localization Sequence

A
  • two short stretches of basic amino acids and 7-10 amino acid long spacer sequence (ie: KR[PAATKAGQA]KKKK)
25
Q

Karyoferin

A

family of receptor proteins responsible for moving macromolecules into or out of nucleus

26
Q

Importin

A
  • type of karyoferin
  • brings macromolecules into nucleus
27
Q

Exportin

A
  • type of karyoferin
  • bring macromolecules out of nucleus
28
Q

importin a

A
  • subunit of importin
  • recognizes and binds to basic residues in ‘cargo’ protein’s NLS
29
Q

Importin B

A
  • subunit of importin
  • binds to cytoplasmic filament at NPC
30
Q

Ran-GTP

A
  • active form
  • concentration higher in the nucleus and lower in the cytoplasm
31
Q

Ran-GDP

A
  • inactive form
  • concentration higher in cytoplasm and lower in the nucleus
32
Q

GEF

A
  • Nuclear protein that promotes conversion of Ran-GDP to Ran-GTP
  • maintains high Ran-GTP in nucleus (promotes GTPase activity of Ran)
33
Q

GAP

A
  • cytoplasmic protein that promotes hydrolysis of Ran-GTP to Ran-GDP
  • maintains low Ran-GDP in cytoplasm
34
Q

Nuclear Export Signal

A
  • nuclear-to-cytoplasm targeting
  • necessary and sufficient for this type of targeting
  • most common NES consists of leucine-rich motif (-LxxLxxL-)
35
Q

Piggyback nuclear protein import

A
  • 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
Q

Cyclin

A
  • 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
Q

Cyclin-Dependent Kinases

A
  • 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
Q

Open Mitosis

A
  • higher eukaryotes
  • nucleus completely disassembles by metaphase
  • two daughter nuclei reassemble during end of mitosis
39
Q

Closed Mitosis

A
  • lower eukaryotes
  • nucleus remains intact during mitosis
39
Q

Proteasome

A
  • degrades pre-existing cyclin proteins after start of M phase

MCB2050 (5 decks)

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