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Lecture 18

MCD BIO 165A Lecture 18: lecture 18 nucleusPremium

8 pages70 viewsFall 2018

Department
Molecular, Cell, and Developmental Biology
Course Code
MCD BIO 165A
Professor
arispe
Lecture
18

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lecture 18
nucleus
chromosome location not random
chromosome rearrange and are dynamic
structure
envelope: limit of the nucleus; separates nucleus from cytosol
- continuation with ER, and is the cisternae from ER
- double membrane
- translation can occur on nuclear envelope
- has nuclear pores
complex units
enables transport, to and from nucleus
main function of nucleus: regulation of trafficking
e.g. ribosome subunits needs to be exported to cytosol
condensed nucleoli
- can have several in a cell (≤4)
- function: site of rRNA synthesis
chromatin: DNA material, associated with protein
- chromatin = DNA + protein (mostly histones, binding noncovalently to DNA)
nucleoplasm
- cytoplasm of nucleus; fluid where solutes dissolved
- has elaborate nucleus skeleton (mostly intermediate filaments (mostly lamins
providing shape))
if expose nucleus to detergent, nucleus still keeps the shape -> not nuclear
membrane keeping the shape, nucleus skeleton keeps the shape!
Nuclear envelope
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double membrane
blue balls: ribosomes on rough ER, translating (secreted or ER resident proteins)
- proteins in nucleus made in cytosol & imported into nucleus
- anything made in ER contains peptidase signal sequence; 90% of those are either
transmembrane proteins or secreted
- proteins remaining in cell made in cytosol
transmembrane proteins critical in communication between nucleus & rest of cell
- actin with intermediate filaments
- Nesprin family proteins bridge cytoplasm (IF?) with nucleus transmembrane proteins
Continuum of information transmitted by individual proteins from outside into
nucleus
Physical forces cell sensing can be sensed by nucleus, affecting chromatin &
transcription of genes
Nucleus adapts shape of cell e.g. elongated vs non-elongated
Inner surface of nuclear envelope lined by nuclear lamina; interconnected with
transmembrane proteins
- Lamina is thick condensation of lamin -> shape!
Nuclear pores on there very complicated, essential in trafficking regulation
Specialized transmembrane proteins specific to nuclear envelope e.g. sun binding
Nesprin, which binds intermediate filaments
Nuclear lamina
Composed of condensed lamins
Shape
- Mutation in lamin -> abnormal shape of nucleus
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- mutation leads to sped up aging -> die from cardiovascular disease, smooth muscle
cell degeneration
- Integrity of nuclear lamina regulated by phosphorylation/dephosphorylation.
- lamin types (A, B, C) in nucleus can vary
nuclear pore complex
contained in nuclear pore; made up of different proteins; most common protein is
nucleoporins
enables communication between cytosol & nucleus
highly abundant & large
nuclear pore contains nuclear pore complex (NPC) that appears to fill the pore like
stopper
association of allows protein around 40kD to pass thru, and also ribosomal subunits
cytoplasmic filaments (proteins) critical for interacting importins (involved in nuclear
import)
cytoplasmic ring interacts with central scaffold complexes, where nucleoporins are
located
- nucleoporins form nuclear basket provides structure to nuclear pore
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