1. The Nucleus between the nucleus and cytoplasm
The nuclear envelope and traffic
Internal organization of the nucleus
The nucleolus
The nucleus during mitosis

2. The Nuclear Envelope and the Traffic

3. nuclear pore complexes
The inner and outer nuclear membranes are joined at nuclear pore complexes (arrow)要注意它叫做complex呦因為它有50-100個proteins.
Figure 8.1 The Nuclear Envelope
nuclear pore complexes
Nuclear envelope到底是幹嘛用的？
The presence of nucleus allows gene expression to be regulated by posttranscriptional mechanisms, such as alternative splicing. 例如在原核生物transcription and translation同時發生就不可能有posttranscriptional regulation. Separation of the genome from the sites of mRNA translation thus plays a central role in eukaryotic gene expression.
\Figures_Hi-res\ch08\cell3e08011.jpg
Separation of the genome from the sites of mRNA translation thus plays a central role in eukaryotic gene expression.

4.  functionally similar to
The nuclear envelope consists of two nuclear membrane, an underlying nuclear lamina, and nuclear pore complexes.
The outer membrane is functionally similar to the membranes of the ER (see Ch.9但ER membrane 有translocon等啊妳nucleus membrane 又沒有) and has ribosomes bound to its cytoplasmic surface.
 functionally similar to

5. nuclear lamina  an attachment site for…
The continuity of the outer nuclear membrane with ER. So the space between the inner and outer nuclear membranes is directly connected with the lumen fo the ER.
The inner nuclear membrane is lined by the nuclear lamina, which serves as an attachment site for chromatin (nuclear lamina 只是serve chromatin attachment site?).
nuclear lamina  an attachment site for…
\Figures_Hi-res\ch08\cell3e08013.jpg

6. Figure 8.2 Electron Micrograph Showing Nuclear Pores
\Figures_Hi-res\ch08\cell3e08020.jpg

7. a meshwork of filaments underlying the inner nuclear membrane
The lamina is a meshwork of filaments underlying the inner nuclear membrane and extending into the interior of the nucleus. It provides structural support to the nucleus.
前有講到
“nuclear lamina serves as an attachment site for chromatin”這是 provided by a much more loosely organized matrix of nuclear lamins extends into the interior of the nucleus.
Figure 8.3 Electron Micrograph of the Nuclear Lamina
a meshwork of filaments underlying the inner nuclear membrane
\Figures_Hi-res\ch08\cell3e08030.jpg

8. 60- to 80-kd fibrous proteins lamin A, B1, B2, C
The nuclear lamina is composed of one or more related proteins called lamins. Most mammalian cells contain four different lamins, designated A, B1, B2, and C (到底是誰跟誰associate在一起？).
All the lamins are 60- to 80- kd fibrous proteins related to the intermediate filament proteins of the cytoskeleton.
Like intermediate filament proteins, lamins associate with each other to form filaments.
Figure 8.4 Model of Lamin Assembly
60- to 80-kd fibrous proteins
lamin A, B1, B2, C
coiled-coil 
\Figures_Hi-res\ch08\cell3e08040.jpg

9. Prenylation of C-terminal Cyteine Residues
The association of lamins with the inner nuclear membrane is facilitated by the posttranslational addition of lipid-in particular, prenylation of C-terminal cyteine residues.
Prenylation of these proteins proceeds by three steps. First, the prenyl group is added to a cysteine located 3 a.a. from the carboxyl terminus of the polypeptide chain. The prenyl groups added in this reaction are either farnesyl (15c) or geranyl-geranyl (20 carbons). The a.a. following the cyteine residue are then removed, leaving cysteine at the carboxy terminus. Finally, a methyl group is added to the carboxyl group of the C-terminal cysteine residue.
Prenylation of C-terminal Cyteine Residues

10. Pore Complexes 20 kd Figure 8.5 Molecular Traffic through Nuclear 9 nm
Figure legend:
Small molecules are able to pass rapidly through open channels in the nuclear pore complex by passive diffusion (凡小於20 kd，即使是proteins，會藉所謂open aqueous channels, estimated to have diameters of approximately 9 nM). Macromolecules (指的是RNAs and proteins) are transported by a selective, energy-dependent mechanism that acts predominantly to import proteins and export RNAs (不是雙向的喔). text裡又講 many proteins shuttle continuously between the nucleus and cytoplasm.
Figure 8.5 Molecular Traffic through Nuclear
Pore Complexes
9 nm
20 kd
Structure:
Extremely large with a diameter of about 120 nm.
Molecular mass of approximately 125 million daltons ( kd)
In vertebrates, the nuclear pore complex is composed of 50 to 100 different pore proteins, most of which are present in multiple copies. kd
proteins
\Figures_Hi-res\ch08\cell3e08050.jpg

11. Nuclear Pore Complexes
Figure legend:
Isolated nuclear pore (這不是在自然狀況下看到的情形!) complexes appear to consist of 8 subunits surrounding a central channel
Text:
Visualization of nuclear pore complexes by electron microscopy reveals a structure with eightfold symmetry organized around a large central channel.
Figure 8.6 Electron Micrograph of
Nuclear Pore Complexes
eightfold symmetry organized around a large central channel.
\Figures_Hi-res\ch08\cell3e08060.jpg

12. Figure legend:
Nuclear pore complex構造
8 spokes attached to cytoplasmic and nuclear rings. The spoke-ring assembly
surrounds a central channel. 由cytoplasmic ring 延伸出 cytoplasmic filaments,由
nuclear ring延伸出nuclear basket.
Figure 8.7 Model of the Nuclear Pore Complex
Changes in the conformation of the central channel during the
passage of macromolecules change its opening from 9 nm to
as large as 40 nm (所以並不是每回都開到最大), which is wide enough to accommodate the
largest particles able to cross the nuclear envelope.
from 9 nm to as large as 40 nm
\Figures_Hi-res\ch08\cell3e08070.jpg

13. (NLS) Figure 8.8 Nuclear Localization Signals basic or classic NLS
最早發現的是Alan Smith in 1984 from simian virus 40 (SV40) T antigen.
Figure legend:
The T antigen nuclear localization signal is a single stretch of
a.a.. In contrast, the NLS of nucleoplasmin is bipartite, consisting
of a Lys-Arg sequence, followed by a Lys-Lys-Lys-Lys sequence
located 10 amino acids farther downstream.
Text:
While many NLS consist of these basic a.a. residues, often
termed the basic or “classic” NLS, the amino acid sequences
and structures of other NLS vary considerably.
Figure 8.8 Nuclear Localization Signals
(NLS)
basic or classic NLS
\Figures_Hi-res\ch08\cell3e08080.jpg

14. Key Experiment 8.1 Identification of Nuclear Localization Signals
The viral protein SV40 T antigen was used s a model for studies of nuclear localization in animal cells. T antigen is a 94-kd protein that is required for SV40 DNA replication and is normally localized to the nucleus of SV40-infected cells.
A mutant with a deletion of a.a. 127 to 132 remained in the cytoplasm. Thus a.a. sequence extending from residue 127 to 132 appeared to be responsible fro nuclear localization of T antigen.
Figure legend:
Cells were microinjected with plasmid DNAs encoding chimeric proteins in which SV40 a.a. were fused to pyruvate kinase. Cellular localization of the fusion proteins was then determined by immunofluorescence microscopy. (A) the fusion protein contains an intact SV40 NLS 126 to 132. (B) deletion of a.a. 131 and 132.
Key Experiment Identification of Nuclear Localization Signals
immunofluorescence mi´croscopy
\Figures_Hi-res\ch08\cell3e08ke010.jpg

15. Nuclear Pore Complex      Figure 8.9 Protein Import through the
Two types of proteins play critical roles in protein import through the nuclear pore complex: a nuclear transport receptor and a small GTP-binding protein called Ran, which is related to the Ras.
There are two types of nuclear transport receptors (Karyopherins): importins and exportins.
Figure 8.9 Protein Import through the
Nuclear Pore Complex  
During protein import, a specific importin recognizes the NLS on the cargo protein. Its ability to do this is facilitated by interacting with Ran.
The conformation and activity of Ran is regulated by GTP binding and hydrolysis.
There is a gradient of Ran/GTP across the nuclear pore. This gradient of Ran/GTP is thought to determine the directionality of nuclear transport.
Protein import through the nuclear pore complex can be divided into a five-step cycle.
 binding of importin-Ran/GDP complex to the cargo protein (但 importin and Ran是何時bind在一起的？)
 this cargo-receptor complex binds to the proteins in the
cytoplasmic filaments of the nuclear pore complex. Transport then proceeds by sequential binding to the nuclear pore proteins located further and further toward the nuclear side of the pore complex.
 the exchange of GDP for GTP causes a conformational change of the importin and displaces the cargo proteins
 the importin-Ran/GTP complex is exported back through the nuclear pore complex (export沒有binding to nuclear pore complex proteins了？).
 the final step occurs in the cytoplasm where the GTP is hydrolyzed to GDP to regenerate the Ran/GDP necessary for another round of transport.  
\Figures_Hi-res\ch08\cell3e08090.jpg
GEF: guanine nucleotide exchange factor
GAP: GTPase activating proteins 

16. Table 8.1 Karyopherins with Known Substrates
\Figures_Hi-res\ch08\cell3e08t010.jpg

17. Many exportin are also members of the karyopherin protein family.
Ran/GTP promotes the formation of stable complexes between exportins and their cargo proteins, whereas it dissociates the complexes between importins and their cargos.
所以說由此可知 Ran/GTP promotes the formation of satble complexeds between exportins and their cargo proteins, whereas it dissociates the complexes between importins and their cargos.
Figure Nuclear Export
\Figures_Hi-res\ch08\cell3e08100.jpg

18. Figure 8.11 a novel means of controlling gene expression
Regulation of transcription factors import to, and export from, the nucleus is a novel means of controlling gene expression.
Figure a novel means of controlling gene expression
\Figures_Hi-res\ch08\cell3e08110.jpg

19.  RNP Figure 8.12 Transport of a Ribonucleoprotein Complex
RNAs are transported across the nuclear envelope as ribonucleoprotein
complexes (RNPs)
Figure legend:
Insect salivary gland cells produce large ribonucleoprotein complexs, which contain 35 to 40-kd of RNA and have a total mass of approximately 30 million daltons. This series of electron micrographs shows the attachment of such an RNP to a nuclear pore complex (A) and the unfolding of the RNA during its translocation to the cytoplasm.
Figure Transport of a Ribonucleoprotein Complex
 RNP
\Figures_Hi-res\ch08\cell3e08120.jpg

20. Cytoplasm Figure 8.13 Transport of snRNAs between Nucleus and
RNAs are transported as ribonucleoprotein complexes (RNPs)
Pre-mRNAs and mRNAs are associated with a set of at least 20 proteins (forming a pre-mRNA-protein complex) throughout their processing in the nucleus and eventual transport to the cytoplasm.
Ribosomal RNAs, see Fig. 8-28
For tRNAs, the specific proteins that mediate nuclear export have not been identified.
Many small RNAs (snRNAs and snoRNAs), function within the nucleus as components of the RNA processing machinery.
Figure Transport of snRNAs between Nucleus and
Cytoplasm
\Figures_Hi-res\ch08\cell3e08130.jpg

21. Internal Organization of the Nucleus

23. euchromatin heterochromatins
During interphase, some of the chromatin (heterochromatin) remains highly condensed and is transcriptionally inactive; the remainder of the chromatin (euchromatin) is decondensed and distributed throughout the nucleus.
Cells contains two types of heterochromatin. Constitutive heterochromatin contains DNA sequences that are never transcribed, such as the satellite sequences present at centrosomes. Facultative heterochromatin contains sequences that are not transcribed in the cell being examined, but are transcribed in other cell types.
Figure legend:
The euchromatin is distributed throughout the nuclus. The heterochromatin
is indicated by arrowheads, and the nucleolus by an arrow.
Figure Heterochromatin in Interphase Nuclei
euchromatin heterochromatins
constitutive heterochromatin facultative heterochromatin
\Figures_Hi-res\ch08\cell3e08140.jpg

24. Figure 8.15 Chromosome Organization
\Figures_Hi-res\ch08\cell3e08150.jpg

25. Figure 8.16 Organization of Drosophila Chromosomes
Figure legend:
A model of the nucleus, showing the five chromosome arms in different colors.
The positions of telomeres and centromeres are indicated.
Text:
Although interphase chromatin appears to be uniformly distributed, the chromosomes are actually arranged in an organized fashion and divided into discrete functional domains that play an important role in regulating gene expression. 1885就有人發現, each chromosomes occupies a distinct territory, with centromeres and telomeres attached to opposite sides of the nuclear envelope.
Figure Organization of Drosophila Chromosomes
\Figures_Hi-res\ch08\cell3e08160.jpg

26. in the Mammalian Nucleus
Figure legend:
probes to repeated sequences on chromosome 4 were
hybridized to a human cell. The two copies of chromosome 4,
identified by yellow fluorescence, occupy distinct territories in the
nucleus.
Individual chromosomes also occupy distinct territories within the nuclei of mammalian cells.
Actively transcribed genes are localized to the periphery of these territories, adjacent to channels separating the chromosomes. Newly transcribed RNAs are thought to be released into these channels between chromosomes, where RNA processing takes place.
Much of the heterochromatin is localized to the periphery of the nucleus because proteins associated with heterochromatin bind to the matrix of the nuclear lamina.
Figure Organization of Chromosomes
in the Mammalian Nucleus 
Actively transcribed genes are adjacent to channel 
\Figures_Hi-res\ch08\cell3e08170.jpg   
heterochromatin

27. Fig.4.16 Structure of Metaphase Chromosomes
Figure legend:
An electrongraph of DNA loops attached to the protein scaffold
of metaphase chromosomes that have been depleted of histones.
Like the DNA in metaphase chromosomes, the chromatin in interphase nuclei is organized into loop domains containing approximately 50 to 100 kb of DNA. A good example of this looped-domain organization is provided by the highly transcribed chromosomes of amphibian oocytes, in which actively transcribed regions of DNA can be visualized as extended loops of decondensed chromatin.
These chromatin domains appear to represent discrete functional units, which independently regulate gene expression (see ch. 6). 豈不在講這些chromatin loop 其實就是discrete expression unit

28. Figure 8.18 Looped Chromatin Domains
Text legend:
Light micrograph of a chormosome of amphibian oocytes, showing
decondensed loops of actively transcribed chromatin extending from
an axis of highly condensed nontranscribed chromatin.
A variety of components of the nucleus are localized to discrete subnuclear structures or domains. The nature and function of these nuclear substructure are not yet clear, however, and understanding the organization of functional domains within the nucleus is an incompletely explored area of cell biology (到底怎麼知道有nuclear substructure的？).
Figure Looped Chromatin Domains
\Figures_Hi-res\ch08\cell3e08180.jpg

29. Figure 8.19 Clustered Sites of DNA Replication
Figure legend:
The newly replicated DNA is present in discrete clusters distributed
Throughout the nucleus.
Text:
DNA replication appears to take place in large structures that contain multiple replication complexes (就是說在mammalian nucleus 里有4,000個 origin of replication, 但只有200個discrete DNA replication clusters, 因此每個cluster有40個replication forks ) organized into distinct functional domains, which have been called replication factories.
Actively transcribed genes appear to be distributed throughout the nucleus, but components of the splicing machinery are concentrated in discrete subnuclear structural domains. Rather than being distributed uniformly throughout the nucleus, these components of the splicing apparatus are concentrated in 20 to 50 discrete structures termed nuclear speckles.
Figure Clustered Sites of DNA Replication
BrdU labeled replication factories
nuclear speckles
\Figures_Hi-res\ch08\cell3e08190.jpg

30. Figure 8.20 Localization of Splicing Components
此圖是用anti-snRNPs mAb
Figure Localization of Splicing Components
\Figures_Hi-res\ch08\cell3e08200.jpg

31. Figure 8.21 Cajal Bodies in the Nucleus
Beside speckles, nuclei contain several other types of morphologically distinct structures or domains. Three major types of these nuclear domains are nucleoli, Cajal or coiled bodies, and PML bodies.
Cajal or coiled bodies are enriched in small RNPs and are believed to function as sites of RNP assembly. The function of PML bodies is unknown; they are not enriched in RNPs and are not sites of DNA replication or transcription.
Thus, although these nuclear bodies show the presence of sub-structural domains within the nucleus, their functions remain to be fully elucidated.
Figure Cajal Bodies in the Nucleus
nulcear substructure: nuclear speckles, cajal bodies, PML bodies, nucleolus
\Figures_Hi-res\ch08\cell3e08210.jpg

32. nucleolus
The most prominent substructure within the nucleus

33. Figure 8.22 Ribosomal RNA Genes
Figure legend:
Each rRNA gene is a single transcription unit containing the 18S,
5.8S, and 28S rRNA and transcribed spacer sequence. The rRNA
genes are organized in tandem arrays, separated by non-
transcribed spacer DNA.
the human genome contains about 200 copies of the gene that encode 18S, 5.8S, and 28S rRNAs and approximately 2,000 copies of the genes encodes 5S rRNA.
The most prominent substructure within the nucleus is the nucleolus, which is the site of rRNA transcription (所以DNA會跑到nucleolus才能進行rRNA transcription) and processing (rRNA也有processing!), and of ribosome assembly. 所以說the nucleolus is a ribosome production factory (但 nucleolus 本身並不會製造出ribosomal protein).
Recent evidence suggests that nucleoli also have a more general role in RNA modification (不只是跟rRNA有關囉) and that several types of RNA move in and out of the nucleolus at specific stages during their processing.
Transcription of 5S rRNA, which is also found in the 60S ribosomal subunit, takes place outside the nucleolus and is catalyzed by RNA polymerase III.
Figure Ribosomal RNA Genes
a single transcription unit
200 copies vs. 2,000 copies of 5S rRNA genes
ribosome production factory
\Figures_Hi-res\ch08\cell3e08220.jpg

35. Figure 8.23 Nucleoli in Amphibian Oocytes
Figure legend:
The amplified rRNA genes (怎麼用amplified genes?是T/S吧？) of Xenopus oocytes are
clustered in multiple nucleoli.
Text:
Actively growing mammalian cells, contain 5 million to 10 million ribosomes that must be synthesized each time the cell divides (指的是新合成的吧？).
The genes for 5.8S, 18S, and 28S rRNA are clustered in tandem arrays on five different human chromosomes (chromosomes 13, 14, 15, 21, and 22)(200個genes在五個chromosomes上); the 5S rRNA genes are present in a single tandem array on chromosome 1 (2,000個genes在一起？).
In Xenopus oocytes, the rRNA genes are amplified approximately 2000-fold, resulting in about 1 million copies per cell. These amplified rRNA genes are distributed to thousands of nucleoli, which support the accumulation of nearly 1012 ribosomes per oocytes.
Figure Nucleoli in Amphibian Oocytes
Dividing cells needs 10 x 106 ribosomes
thousands of nucleoli, which support the accumulation of nearly
1012 ribosomes per oocytes
\Figures_Hi-res\ch08\cell3e08230.jpg

36. Figure 8.24 Structure of the Nucleolus
Morphologically, nucleoli consist of three distinguishable regions: the fibrillar center, dense fibrillar component, and granular component. These different regions are thought to represent the sites of progressive stages of rRNA transcription, processing, and ribosome assembly.
Following each division, nucleoli become associated with the chromosomal regions that contain the 5.8S, 18S, and 28S rRNA genes, which are therefore called nucleolar organizing regions.
the fibrillar centers
the dense fibrillar compnents
granular component
\Figures_Hi-res\ch08\cell3e08240.jpg

37. Figure 8.25 Transcription of rRNA Genes
rRNA genes are very actively transcribed by RNA polymerase I, allowing their transcription to be readily visualized by electron microscopy
Figure Transcription of rRNA Genes
tandem arrays of rRNA genes
high density of RNA polymerase I
the knobs are formed by U3 small nucleolar RNP binding to the 5’-end of
45S pre-rRNA
\Figures_Hi-res\ch08\cell3e08250.jpg

38. Figure 8.26 Processing of Pre-rRNA
Processing includes
Cleavage
Base modification: methylation, conversion of uridine to pseudouridine
圖中其實ribosomal proteins 早已bind上來了。
Figure Processing of Pre-rRNA
external transcribed spacer
interanl transcribed spacer
U3 small nucleolar RNP
\Figures_Hi-res\ch08\cell3e08260.jpg
U8 snoRNA
U22 snoRNA

40. of Pre-rRNA Figure 8.27 Role of snoRNAs in Base Modification
Figure legend:
The snoRNAs contain short sequences complementary to rRNA.
Base pairing between snoRNAs and pre-rRNA targets the enzymes
that catalyze base modification.
Nucleoli contain more than 300 proteins and a large number (about 200) of small nucleolar RANs (snoRNAs) that function in pre-rRNA processing.
The snoRNAs are complexed with proteins, forming snoRNPs.
Individual snoRNPs consist of single snoRNAs associated with 8 to 10 proteins.
The snoRNPs then assemble on the pre-rRNA to form processing
complexes in a manner analogous to the formation of
spliceosomes on pre-mRNA (要回想Fig. 8.25).
Most of the snoRNAs contain short sequences of approximately 15 nucleotides of complementary to 18S or 28S RNA.
These regions of complementarity include the sites of base modification in the rRNA.
By base pairing, with specific regions of the pre-rRNA, the snoRNAs act as guide RNAs that target the enzymes responsible for ribose methylation or pseudouridylation to the correct site on the pre-rRNA molecule.
Figure Role of snoRNAs in Base Modification
of Pre-rRNA
\Figures_Hi-res\ch08\cell3e08270.jpg

41. Figure 8.28 Ribosome Assembly
The genes that encode ribosomal proteins are transcribed outside the nucleolus by RNA polymerase II, yielding mRNAs that are translated on cytoplasmic ribosomes.
The ribosomal proteins are then transported into nucleolus, where they are assembled with rRNA to form preribosomal particles. The association of ribosomal proteins with rRNA begins while the pre-rRNA is still being synthesized.
While half of the ribosomal proteins are complexed with the pre-rRNA before its cleavage, the remaining ribosomal proteins and the 5S rRNA are incorporated into preribosomal particles as cleavage of the pre-rRNA proceeds.
Figure Ribosome Assembly
\Figures_Hi-res\ch08\cell3e08280.jpg

42. Figure 8.29 The Nucleus during Mitosis
Ch.14 presents a comprehensive discussion of mitosis
在這章我們只 consider the mechanisms involved in the disassembly and re-formation of the nucleus.
The process is controlled largely by reversible phosphorylation and dephosphorylation of nuclear proteins resulting, in part, from the action of Cdc2 protein kinase.
spindle microtubules
Figure legend
Mitosis可分成四個stages-PMAT
During prophase, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down.
At metaphase, the condensed chromosomes align on the center of the spindle.
The daughter chromosomes then move to opposite poles of the spindle (anaphase)
During telophase the chromosomes de-condense and the nuclei re-form.
chromosomes
\Figures_Hi-res\ch08\cell3e08290.jpg

43. Figure 8.30 Closed and Open Mitosis
Some unicellular eukaryotes (e.g. yeasts) undergo so-called closed mitosis.
Figure Closed and Open Mitosis
\Figures_Hi-res\ch08\cell3e08300.jpg

44. Figure 8.31 Dissolution of the Nuclear Lamina
Disassembly of nuclear envelope involves changes in all three of its components: the nuclear membrane are fragmented into vesicles, the nuclear pore complexes dissociate, and the nuclear lamina depolymerizes (有時又叫做dissociate，如下一張之figure legend).
Disassembly of the nuclear lamina results from phosphorylation of the lamins, which caused the filaments to break down into individual lamin dimers (不會更小). Treatment of isolated nuclei with Cdc2 has been shown to be sufficient to induce depolymerization of the nuclear lamin (雖然它說other protein kinases activated in mitosis 也會phosphorylate lamins).
Figure Dissolution of the Nuclear Lamina
\Figures_Hi-res\ch08\cell3e08310.jpg

45. Figure 8.32 Breakdown of the Nuclear Membrane
Figure legend:
As the nuclear lamina dissociates, the nuclear membrane fragments into
vesicles. The B-type lamins remain bound to to these vesicles, while lamins A
and C are released as free dimers (如果先前不是A與C形成dimers，為何dissociate
後會變成AC dimer).
前面有講到 The process (指的是disassembly and re-formation of the nucleus) is controlled largely by reversible phosphorylation and dephosphorylation of nuclear proteins resulting, in part, from the action of Cdc2 protein kinase.
還有哪些phosphorylation?
The nuclear pore complex also dissociate into subunits as a result of phosphorylation of several nuclear pore proteins. Integral membrane proteins are also phosphorylated at mitosis, and phosphorylation of these proteins may be important in vesicle fomation and in dissociation of the nuclear membrane from both chromosomes and the nuclear lamina.
Figure Breakdown of the Nuclear Membrane
\Figures_Hi-res\ch08\cell3e08320.jpg

46. Figure 8.33 Chromosome Condensation
The interphase chromatin, which is packed into nucleosomes, condenses approximately 1000 x further to form the compact chromosomes seen in mitotic cells.
DNAs in this highly condensed state can no longer be transcribed, so all RNA synthesis stops during mitosis. As the chromosomes condense and transcription ceases, the nucleolus also disappears.
Figure Chromosome Condensation
\Figures_Hi-res\ch08\cell3e08330.jpg

47. The mechanism of chromosome condensation during mitosis is not understood. 但它的structure是知道的; the condensed DNA in metaphase chromosomes is organized into large loops, each encompassing about a hundred kb of DNA, which are attached to a protein scaffold.
Condensation mechanism不知但有很多phosphorylation
histone H1 is a substrate for the Cdc2 during chromosome condensation. However, recent experiments showed that phosphorylation of histone H1 is not required for chromosome condensation. In contrast, phosphorylation of H3 is required for condensation.

49. SMC and condensin
structural maintenance of chromosomes

50. Figure 8.34 Re-Formation of the Nuclear Envelope
The first step in reassembly of the nuclear envelope is the binding of membrane vesicles to chromosomes, which may be mediated by both integral membrane proteins and B-type lamins. The vesicle then fused to form a double membrane around the chromosomes.
This is followed by reassembly of the nuclear pore complexes, re-formation of the nuclear lamina, and chromosome de-condensation.
Figure Re-Formation of the Nuclear Envelope
\Figures_Hi-res\ch08\cell3e08341.jpg

51. \Figures_Hi-res\ch08\cell3e08343.jpg

52. Molecular Medicine 8.2 Nuclear Lamina Diseases
\Figures_Hi-res\ch08\cell3e08mm010.jpg