cell cycle pt.1 +cyclins and cdk general

How does each phase of the cycle take

M 1h, g1 11h, s 8h 62 4h so the quickest is mitosis the slowerst is g1

Describe what happens during prophase

During prophase 1. Formation of spindle

2. The cromosomes condends

Describe prometaphase

In prometaphase the nuclear envelope breaks down!

Chromosomes attach to the spindle via kinetocores

Metaphase

Chromosomes alined,

Kinetocore attahce sister chromaties to opposite pole of the spindle

Anaphase

Sister chromatis separate pulled in opposite directions

Spindle pole moves outward

Shortening of the kinetocore microtubule

Telophase

Here the two sets of daugter chromomes are at the poles and decondense

Nuclear envolope reasseblleds foming 2 nuclei

Cytokinesis

Completed nuclear envolpe surroundes decondesing chromosomes

The contractile ring of actin and myosin

What are cyclicing cell?

Differentiated cell that divide?

Diff. Cell that do not divide?

Cycling cells divide regukary as,, stem cells

Differentiate that divide if induced es, fiboblast, lymphocytes

Differentitaed non dividing: muscle cells, red blood cells, neurons

How can you study cell cycle progression?

1. Flow cytometry with day that stains dna

2. Microsocpu of cell labelled with BRDU

Which are the check point? Molecular binary swithches allow it to be reversible?

Which are the 3 main checkpoints

1. Start or restriction at end of g1

To enter the cell cycle and decide if the cell commis to dna replication

2. G2/m transitiion: does the cell have verithing ok to enter mitosis?

3. Metaphase anaphase transition

Triggers anaphase

Whcihc signals control the g1 checkpoint?

When is the cell sent to g0?

The are both intrinsic and external factors

Internal: cell size

External: nutrients and gf

No gf is go back to g0

What is the definition of immortalised cells?

Cell used inthe lab as a simple model for more complex systems and can be grown for prolonged peridos in vitro. ( some normal some equivalent to cancer cells)

Anchorage dependency means that to divide the cell must?

Who provides this?

What if the attachement is lost?

What happens when the cytoplasm is too croweded?

It must be anchored this is provided by integrins and adhesion protein s

Too chrowded stop for contact inhibition

When do sell arrest the cycle in g2? So after dna replication?

When the enviroment is not favourable. Then progression to m phase is triggered by horons as in OOCYTES!

To avoid erorrs whih are the 2 important chcekpoint thtat ptherwise block the cycle?

1. DNA DAMAGE CONTROL

2. SPINDLE ASSEMBLY CHECKPOINT ( stops mitosis in METAPHASE if chromosomes are not aligned on the spindle)

In the case there are spindle assembly errors in which phase is the cyle arrested

Metaphase

What are the 3 experiments that allow to identify the cell cycle regulators?

1. 1971 frog oocytes arrested in g2 could be induced to enter m phase if hormonllay stimulated

Factor found: mpf maturatin promoting factor also presnet in somatic cells where it induces mitosis

2. Genatic analyses of yeast

Mutants that were defective in cdc cell division cycles

Found: CDC GENES are needed to start and enter mitosis theu encode PROTEIN KINASE ( CDK1 IN ALL EUK.=

Which are the cycle regulators?

Cyclins which levels change during the cycle

Cdk which are kinase but need cyclins to be active

G1 cyclins help go fromg0 to g1

G1/s cyclins allow to push it into s

S cyclins promote repliction

M mitosis

Which factor allows the cell to go to mitosis?

Which cdk and cyclin forms it?

Trough which experiment was this factor discovered?

MPF maturation promoting factor which in somatic cells allow to enter mitosis

Formed by regulatory subuint of cyclin B and catalitic sub. Cdk1

Why do cdks can have different effects?

What does plasticity mean in this case

Cdk can have different effects beauces the substrate changes

Plast. Means that in case of loss dk/cylcins can substitue other kinds

What are 4 ways to regulate cdk

A. The most simple

B, activatory phoph.

C. Inihbitory phosph….

D. Binding of inibitory proteins to

A. By binding with cyclin

C. By ACTIVATORY PHOPHORILATION OF THREONIN POS.161

By inhibotry phoph. Of TIROSIN catalized by WEE1 kinase

Binding inhibitory proteins to cdk inhibitors

Which genes discovered with the analyses of yeasts ( where they were muteted) are requiredd to passage start point and encode kinase

CDC this protein kinase is in ALL EUKARYTOES: CDK1

When is MPF actiity low? And high?

What about cycli b when is it degradated?

Mpf stands for mitotic promoting factor so is high in mitosis and low in interphase

Cyclin b acculates during interphase and is degradated in mitosis

When cdk are not active anbd cyclin is not bind what is the conformation?

When is it considered PARTILAIIY ACTIVE?

Whne is not bind: loop obscures cdk

Wen it binds with cyclin it moves the loop and this is partial activation

When is cdk considered FULLY ACTIVE

It happens when after the bind with a cyclin

A SEPARATE KINASE CAK ( cdk activating kinase) phophorilates the AA NEAR THE ACTIVE SITE FOR CDK ( threonin 161)

How is cdk inhibited leading to its accumulation of INACTIVE cdk1 with cyclin b during g2?

By wee1 that phopohrilates it an inhibits it this is inhibitory phophorylation

What is the function of cdc25 phophates

Cdc25 inhibits cdk1

Dephophorilation by cdc25 activates cdk1

During g2 how is inibiotory phophorilation of cdk1 work?

What hibits it by phophorilating it?

Wha activates cdk1 by dephophirlating it?

To inhibit by phophorilation use wee1 kinase

Cdc25 activates cdk1 by dephophorilating it

What are CKI

In which phase is it mainly used

Cki are cyclin cdk inhibitors

CKI binding make a change in cdk active site structure

IN THE BEGGINING G1/s

How is cdk activation terminated

By degradating cyclin trough negative feedback: apc/c ubiquitin ligase make cyclins to be degratadated and STOPPING MITOSIS

After thata cdk1 is deactivated by dephophrylating thresoin 161

Which are the two ubiquitin ligases that control the cell cycle?

Which degradates cyclins?

Which degradates cdk Ihibitor proteins?

Which changes during the cycle?

1. Which stays constant

APC/C CHANGES DURING CELL CYCLE

Is for cyclins and securins

It is controlled by the change in association of activating subuints

SCF is CONSTANT

It is controlled by changes in the phophorilation states of the target protein

Target is CDK i inhibitors

What are SCF what controlls them? And how do they change during the cycle?

Scf are ubiquitin ligase fro cDK Inhibitors

Do not change during cycle

Controlled by variation in phophorilation states of target proteins