1. No category

細胞生物學導論
Cell Nucleus and Cell Cycle
解剖所 龔秀妮
2014 Kung
Cell nucleus
 Structure
 Components
 Function
the boss of a cell, information store
Nucleus
Eukaryotic cell
Prokaryotic cell
The importance of nucleus
Information store
The structure of nucleus
Nuclear lamina
Euchromatin (常/真染色質)：基因密度高，製作蛋白質。
Heterochromatin (異染色質)：satellite sequences，不具遺傳活性，包括著絲
粒、端粒及雌性體內去活化的X染色體（巴爾氏體/Barr body, 1949）。
The structure of nucleus-nuclear envelope
Chi et al. Journal of Biomedical Science 2009 16: 96
The structure of nucleus-nuclear pore
A cross section of
a nuclear pore on
the surface of the
nuclear envelope.
(1) Nuclear
envolope
(2) the outer ring
(3) spokes
(4) basket
(5) filaments
Nuclear Pore Complex (NPC); Transport into and out of the Nucleus
(nucleoporins)
30-50nm
Pore
complex
nuclear
localization
signal
Nuclear transport
Importin (nuclear import receptor)
RanGAP
nuclear pore
complex
RanGTP
NTF2
(importin)
RanGDP
Exportin -- nuclear export signal (NES)
The structure of nucleus-nuclear envelope
Chi et al. Journal of Biomedical Science 2009 16: 96
LAP: lamin associated protien
LBR: lamin binding receptor
Nesprin
Emerin
BAF: autointegration factor
- bind to chromatin
HP1
Nuclear lamina –
intermediate filament
Maturation promoting factor
Dynamics of nuclear lamina
What is inside the nucleus?
Nucleolus – rDNA
 Found in 18th century, but understand the
function in 1960
 Single or several in number
 Produce ribosome
 Human：usually one, but become 10 in cell
division
Swiss mouse embryo fibroblast cell stained with fluorescent probes targeting the nucleus
(blue), mitochondria network (red), Golgi complex (green) and nucleoli (magenta).
snoRNA
small nucleolar RNA
Functions of
Nucleolus
 Granular component
(pars granulosa) :
ribosomal subunits
 Fibrillar component
(pars fibrosa) :
rRNA molecules
and associated
proteins
5.8S rRNA
5.0S rRNA
28.0S rRNA
Proteins
18S rRNA
Proteins
Figure 6‐47 Molecular Biology of the Cell (© Garland Science 2008)
nucleus
Government building
ribosome
factory
nucleolus
main office
protein
product
Nucleolar cycle
Nucleolar fusion (after mitosis) --fibroblast
Figure 6‐46 Molecular Biology of the Cell (© Garland Science 2008)
Nucleostemin:
• p53 binding protein
• Regulate cell cycle
• Decreased in differentiated cell
nucleostemin
• Stem cell marker
• Viral replication
Actin
nucleostemin
DAPI
DAPI
What is inside the nucleus?
Chromosome
1933年-諾貝爾生理醫學獎 (Thomas Hunt Morgan)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
DNA+protein
telomere
23 pairs-22 homologous/1sex
telomerase
chromatine
condensation
chromosome
Karyotype (核型)
Cytogenetic testing
FISH
(Fluorescence in situ hybridization)
What is inside the nucleus?
Other subnuclear bodies
Structure name
Structure diameter
Cajal bodies
0.2–2.0 µm
RAFA and PTF domains
5 µm
PML bodies
0.2–1.0 µm
Paraspeckles
0.2–1.0 µm
Speckles
20–25 nm
What is inside the nucleus?
Other subnuclear bodies
Cajal bodies and gems
1903 nucleolar accessory bodies
coilin
RNA processing, snoRNA maturation, histone mRNA modification
Subnuclear structures
Fibrillarin (snoRNPs)
Nucleolus, Cajal body
Bulk chromatin
Interchromatin
granules (Speckles)
Protein coilin
Cajal body
Figure 6‐48 Molecular Biology of the Cell (© Garland Science 2008)
 Cajal bodies
 GEM (Gemini of Cajal bodies)
 Speckles (interchromatin granule
clusters)
Normal nucleus
Abnormal nucleus
nuclear lamina heterochromatin
nucleoli nuclear matrix proteins (NMP)
promyelocytic leukaemia (PML) body
Normal nucleus. The nucleus is
bounded by the nuclear lamina
(purple), a proteinaceous layer made
of the lamins and associated proteins.
The lamina is connected on its
cytoplasmic face to the doublemembrane nuclear envelope. On its
inner surface, the lamina binds to
chromatin and in most cell types the
lamina-associated chromatin
domains correspond to
heterochromatin (green). Another key
site of heterochromatin formation is
at the surface of the nucleoli (yellow).
Typically, 1–3 nucleoli are present
per nucleus. These have a wellestablished role in ribosome
biogenesis, but seem to also be
involved in other functions such as
mRNA transport, p53 metabolism
and the control of proliferation. The
nuclear matrix (black internal network;
nuclear matrix proteins (NMP)
indicated by small blue circles) is the
non-chromatin nuclear scaffolding
that participates in the spatial
organization of chromatin and the
positioning of nuclear molecules and
substructures. One such substructure
is the promyelocytic leukaemia (PML)
body (red). The PML growth and
tumour suppressor is an essential
component of this doughnut-shaped
multiprotein complex. One important
function of PML and the PML body is
the control of various apoptotic
pathways. The figure outlines only
those nuclear structures discussed in
the text.
Cell cycle
Progress
Regulation
The importance of nucleus in the maintaining of life
Cell growth – size
Cell proliferation – divide
Cell proliferation – cell cycle
daughter cell
O: outside of the cell cycle
Static cells:
CNS, cardiac muscle cell
Stable cells:
periosteal, perichondrial, smooth muscle, endothelial cell,
injury induced proliferation
Slowly renewing cells:
smooth muscle of most hollow organ,
epithelial cells of the lens
Rapidly renewing cells:
epithelial cells and dermal fibroblast of the skin
Interphase: G1+S+G2
drugs
mutagen
7-10h
Enzyme synthesis
Centriole  2 centrioles
9-12h
24h
3-5h
1h
Mitosis:
 Animals – open mitosis
(nuclear envelope
break down)
 Fungi/yeast
– close mitosis
(intact nucleus)
 Prokaryotic cells
– binary fission
(no nucleus)
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Early Prophase and Late Prophase
prometaphase
Figure 2.18 (1 of 2)
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Metaphase and Anaphase
Figure 2.18 (2 of 2)
State
Abbreviation Description
quiescent/
Gap 0
senescent
G0
A resting phase where the cell has left the cycle
and has stopped dividing.
Gap 1
G1
Cells increase in size in Gap 1. The G1
checkpoint control mechanism ensures that
everything is ready for DNA synthesis.
Synthesis
S
DNA replication occurs during this phase.
Interphase
Cell
division
Gap 2
G2
Mitosis
M
During the gap between DNA synthesis and
mitosis, the cell will continue to grow. The G2
checkpoint control mechanism ensures that
everything is ready to enter the M (mitosis) phase
and divide.
Cell growth stops at this stage and cellular energy
is focused on the orderly division into two
daughter cells. A checkpoint in the middle of
mitosis (Metaphase Checkpoint) ensures that the
cell is ready to complete cell division.
To control the accuracy and fidelity of cell cycle :
checkpoint surveillance mechanism
Animal: restriction point
Yeast: start point
2001 Nobel Prize
Cyclin –CDK complexes of the cell cycle
control system
Cell Division Cycle
Table 17‐1 Molecular Biology of the Cell (© Garland Science 2008)
Cyclin –CDK complexes of the cell cycle
control system
Cyclin D/E
Cyclin A
Cyclin B
Anaphase-Promoting Complex
CDK: constantly expressed
Figure 17‐16 Molecular Biology of the Cell (© Garland Science 2008)
G1 phase
S phase
G2 phase
M phase
D
4
G2/M transition
Cyclin B + CDK1
G1/S transition
Cyclin E + CDK2
800-1200 genes
• Nuclear envelope
breakdown
• Initiation of prophase
Check points !!
Cell death (apoptosis)
Dysfunction: cell cycle arrest
Cell growth (tumor)
Activity of S. cerevisiae cyclin-CDK complexes
through the course of the cell cycle
Activity of mammalian cyclin-CDK complex
through the course of the cell cycle
Inhibitors of cell cycle
Cip family:
(CDK inhibitory protein)
p21, p27, p57
Kip family:
(Kinase inhibitory protein)
CAK, Wee1, Cdc25
Ubiquitin ligase:
APC, cdc20, cdh1, SCF
TGFβ
p27
Cip family:
(CDK inhibitory protein)
p21, p27, p57
Kip family:
(Kinase inhibitory protein)
CAK, Wee1, Cdc25
Ubiquitin ligase:
APC, cdc20, cdh1, SCF
Figure 17-18 Molecular Biology of the Cell (© Garland Science 2008)
CAK
Cip family:
(CDK inhibitory protein)
p21, p27, p57
Kip family:
(Kinase inhibitory protein)
CAK, Wee1, Cdc25
Ubiquitin ligase:
APC, cdc20, cdh1, SCF
Figure 17-20a Molecular Biology of the Cell (© Garland Science 2008)
Figure 17-20b Molecular Biology of the Cell (© Garland Science 2008)
Anaphase Promoting
Complex/Cyclosome
Stem Cell Factor
Table 17‐2 Molecular Biology of the Cell (© Garland Science 2008)
Synchronization of cells in culture
S arrest
5-fluorodeoxyuridine
G1 arrest
Serum starvation
Thymidine
aphidicolin
G2/M arrest
Colchicine
nocodazole
Cell cycle analysis
Stain of DNA:
1. Acridine Orange
2. Propidium Iodine
3. DAPI/ Hoechst
2N
4N