Cell Cycle, Cell Death, & Cancer Flashcards
What is the 2nd leading killer in the United States?
Cancer
This stage of mitosis is when the cell begins to assemble the mitotic spindle, and a set of microtubules extend from the centromeres which will later attach to the chromosomes.
Prophase
At this stage of mitosis, the nuclear envelope disintegrates, and the microtubules of the mitotic spindle attach to the chromosomes.
Prometaphase
At this stage of mitosis, the chromosomes are aligned on the mitotic spindle. There is a pause here to allow all chromosomes to become attached.
Metaphase
At this stage of mitosis, the cohesion proteins which bind the sister chromatids together are cleaved and the chromosomes are pulled apart by the mitotic spindle.
Anaphase
At this stage of mitosis, the nuclear membrane reconstitutes around each set of chromosomes.
Telophase
The presence of sufficient stimulus (conditions) will encourage a cell recently formed by mitosis to remain in the active growth-and-division cycle. The absence of these stimuli will trigger the default decision to proceed from mitosis into the ______, quiescent state.
G0
In this cell cycle phase, there is quiescence, intact proliferation capacity, and non-cycling.
G0 phase
In this cell cycle phase, it is the duration between completion of cell division and initiation of DNA replication where cells start building cell mass.
G1 phase
In this cell cycle phase, DNA replication takes place.
S phase
In this cell cycle phase, it is the duration between completion of DNA replication and initiation of cell division.
G2 phase
In this cell cycle phase, mitosis occurs.
M phase
How do we know at what phase cells are in during the cell cycle?
Population of cells is labeled with fluorescent dye that binds DNA. Cells are passed through flow cytometer, which measures fluorescence intensity. Data are plotted as cell number vs fluorescence intensity, which is proportional to DNA content. Distribution shows two peaks, 2n contents are at peak 1 which are cells in G1 phase and 4n contents are at peak 2 which are cells in G2 and M phases. Cells in S phase have contents between 2n and 4n so they fall between the two peaks.
________ is going through the cell cycle phase, while ________ is going from one phase to another.
Progression
Transition
What are the 3 types of regulators involved in the cell cycle?
Cyclins
CDKs (Cyclin dependent kinases)
CKIs (Cyclin dependent kinase inhibitors)
These cyclins are involved in the G1 phase.
Cyclins C, D 1-3, E 1-2, F, G
These cyclins are involved in the S phase.
Cyclin A
These cyclins are involved in the G2/M phases.
Cyclins B 1-2
This cyclin has constitutive expression.
Cyclin H
The (LEVEL/ACTIVITY) of cyclins vary during the cell cycle. CDK (LEVEL/ACTIVITY) is constant, but its (LEVEL/ACTIVITY) varies.
Level
Level
Activity
_____ are dependent on cyclins. They must be bound to cyclin to have kinase activity. Without cyclin, they are inactive.
CDKs
Cyclins and CDKs have a special bond. The ________ _______ is present in all CDKs and is essential for binding of cyclins.
PSTAIRE alpha-helix
Without the cyclin bound (inactive state), the active sit of CDK is blocked by a region of the protein called the ________. The binding of cyclin causes the _______ to move out of active site. This makes the CDK partly active.
T-loop
T-loop
Phosphorylation of the CDK at the T-loop fully activates the enzyme. Phosphorylation is caused by ________.
CAK (CDK activating kinase)
CDKs can be phosphorylated at the cave site (T-loop) which fully activates the enzyme, but it can also be phosphorylated at the roof-site and another site which will inactivate it. These inactivating sites can be dephosphorylated by _________ to reactivate the CDK.
Cdc25 (A, B, or C)
This type of CDK is paired with cyclin A, B1, and B2. It triggers G2 to M transition.
Cdk1
***Cyclin A is synthesized in S and destroyed starting at pro metaphase
***Cyclins B are synthesized in S/G2 and destroyed following the completion of chromosome attachment to the spindle
This type of CDK is paired with cyclins A and E. It triggers the transition of G1 to S.
Cdk2
These block the action of CDKs and ensure tight control and balance of the cell cycle. They bind to both the CDK and cyclin to inactivate. Activated upon cell cycle checkpoint.
CKIs
These types of CDKs are paired with cyclin D1-D3. They are responsible for phosphorylation of the retinoblastoma susceptibility protein in G1 and triggers the passage of the restriction point and cyclin E synthesis in some cell types.
Cdk4
Cdk6
This enzyme has Cdk1 and Cdk2 as substrates and promotes G1 to S transition and G2 to M transition.
Cdc25A phosphatase
This enzyme has Cdk1 as substrate and promotes transition of G2 to M transition.
Cdc25B phosphatase
This enzyme has Cdk1 as substrate and promotes G2 to M transition, and dephosphorylates Cdk1 complexed to cyclins A and B.
Cdc25C phosphatase
______ function by inactivating CDKs through inhibitor binding and phosphorylation interference.
CKIs
This kinase inhibits Cdk activity by phosphorylating the “roof site”.
Wee1
This type of CKI will bind to Cdk and twist the upper lobe, blocking cyclin binding or interfering with ATP hydrolysis.
INK4
When these type of CKIs bind, a loop insinuates into the upper lobe of the Cdk and blocks ATP binding.
p27
p21
This type of CKI is induced by p53 tumor suppressor, and causes cell-cycle arrest after DNA damage.
p21
This CKI will cause cell cycle arrest in response to growth suppressors like TGF-B and in contact inhibition and differentiation.
p27
These are a superfamily member that are often called “small G proteins”. They receive their signal from catalytic receptors that have been activated by their ligand. The overall effects often involve induction of cell proliferation.
Ras
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G1/S transition – When E-CDK2 complexes drive pRb hyperphosphorylation, this liberates E2F transcription factors from pRb control, enabling the E2Fs to trigger increased transcription of the cyclin E and E2F1 genes. This leads to the synthesis of more cyclin E protein and the formation of more E-CDK2 complexes, which function, in turn, to drive additional pRb phosphorylation. At the same time, the newly synthesized E2F1 protein drives its own expression, further amplifying its activity. What kind of feedback does this portray?
Positive feedback
During S phase – Origins of replication are recognized first by the _______, which serves as a landing pad for recruitment of the remaining components. Following this, ______ and _____ function in a concerted fashion to recruit the ______-_____ complex, which is considered the replicative helicase.
ORC1-ORC6
Cdt1
Cdc6
MCM2-MCM7
During S phase – At the beginning of S phase, additional factors (MCM10, CDC45, and polymerases) are recruited and replication can initiates in a fashion dependent on the ______ and ______ kinase activities.
Cdk2
Cdc7
G2/M transition – What complex initiates passage into the mitotic phase?
B-CDK1
At the G1 checkpoint there are two pathways that can be taken after DNA damage that target the activity of cyclin/cdk complexes. Explain these pathways.
1) The slower pathway involves the stabilization of p53 and transcriptional up regulation of p21 which binds and inhibits the Cyclin/Cdk complexes (p16 can also prevent cell cycle progression).
2) The faster pathway acts via the activation of Chk2 and the inactivation of Cdc25. Thus, inhibitory phosphates of the CyclinE/Cdk2 complex can no longer be removed.
In the G2 checkpoints, there are two ATM-dependent checkpoint pathways that are activated. What are these pathways?
1) Chk1/Chk2 target Cdc25 for nuclear export leading to the accumulation of the inactive B-Cdk1 complex
2) Activation of the p53 to p21 CKI pathway will phosphorylate B-Cdk1 complex and inhibit it.
This is the term for a space occupying lesions that may or may not be neoplasms.
Tumors
This is the term for a relatively autonomous abnormal growth with abnormal gene regulation, 2 types: benign and malignant.
Neoplasm
This is the term for a malignant neoplasm (can produce metastasis).
Cancer
This is the term for a secondary growth of cancer at a different location from the primary neoplasm.
Metastasis
This stage of carcinogenesis is irreversible and has no threshold. It involves genotoxic agents including chemicals, radiation, ROS, and viruses. Involves sequence change in cellular DNA. Can be a result of the activation of oncogenes or the inactivation of tumor suppressor genes.
Initiation
This stage of carcinogenesis occurs over a long period of time and is reversible in its early stages. Involves expression through cellular selection and clonal expansion. Threshold exists (time and dose). Inhibition of cell death in initiated cells.
Promotion
This stage of carcinogenesis involves further complex genetic changes (translocations, deletions, gene amplifications). Irreversible changes in gene expression, evolution of karyotypic instability. Results in conversion of benign tumors into malignant neoplasms capable of metastasizing.
Progression
These cellular genes cause a gain of function by stimulating cell division and/or growth. Loss of regulation of these genes lead to enhanced expression of proteins which leads to unregulated cell division and growth (Gas-pedal). Dominant – means only one allele needs to be mutated.
Oncogenes
These cellular genes serve to check or inhibit cell division. Loss of expression of these proteins lead to cell growth or cell division (loss of function/brake-pedal) Recessive – means both alleles have to be mutated for it to occur.
Tumor suppressors
What is a major example of a tumor suppressor gene that can be mutated and cause cancer?
p53
***Also Rb (remember retinoblastoma)
This tumor suppressor gene can inactivated on human chromosome 9p21 in human cancers (2nd most commonly inactivated gene).
p16INK4A
This is the term for the environment of cancer cells that includes cellular components (non-cancerous cells), secretory factors, and extracellular matrix (fibrous proteins and proteoglycans).
Tumor Microenvironment (TME)
What is the primary target of cancer in most approved therapies?
DNA (due to proliferative nature of cancer cells)
(CHEMOTHERAPY/RADIATION) is best for cancer cells which have:
1) Reproductive activity
2) Cells which have longer dividing future ahead
3) Cells with morphology and function are least fixed
Radiation
How does radiation work?
- Direct deposition of energy to break DNA bonds.
- Hydrolysis of water to produce powerful damaging free radicals.
One of the main triggers for cell death is DNA damage, specifically ________ ________ which have long been thought to be the most important for cell killing.
Double-strand breaks
What are the types of cell death?
Apoptosis (programmed cell death – suicide)
Autophagy (Self destruction – digestion)
Necrosis (Explosive disaster)
Mitotic catastrophe
Senescence (Irreversible growth arrest - reproductive cell death)
In this type of cell death, the cell membrane swells and ruptures. The nucleus breaks apart and inflammation is triggered.
Necrosis (dirty death)
In apoptosis, when it is triggered by DNA damage then it causes up regulation of _______. This causes the release of ______ which induces apoptosome formation. This in turn activates Caspase ______, which activates Caspase ________.
BAX/BAK
Cyt C
Caspase 9
Caspase 3, 6, 7
In apoptosis, when it is triggered by receptor signaling then ________ bind to receptor, which forms _______. This then activates Caspase ______, which goes on to activate Caspase _______.
Fas/TNF
FADD
Caspase 8
Caspase 3, 6, 7
This type of cell death is recycling of worn out organelles.
Autophagy
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