Finals Flashcards
Senescent cells
A G0 state in which cells are not able to divide anymore by reaching their limit. Older cells, replicated a lot and can’t do it anymore.
Quiescent cells
In G0 state where they are resting but can still go back to G1
Differentiated cells
Cells in G0 state that are terminally differentiated cells. Specialized to the point where reproduction is no longer an option.
Pulverization
Pulverization (grinding, cutting) of chromosome is found in S phase chromosomes when S phase and Mitotic cells are fused.
Maturation-promoting factor (MPF)
Contain two components:
1) Serine/threonine kinase - phosphorylates
2) cyclin
These two components form a dimer when close to M phase, and together they make the MPF and allow entry into mitosis and helps regulate it.
In yeast cells, cdc2 kinase, cyclin, and phosphorylated Thr161 (reissue on kinase) complex is the MPF.
Cyclin-dependent kinases (Cdks)
MPF-like enzymes. They help orchestrate what goes in inside cells at different points in cell cycle by phosphorylating the kinases and target the right targets and turns things on and allow things to progress in cells.
Cdc2
In yeast, it’s the S/T kinase. Binds with G1/S cyclins to allow into S phase. Binds with mitotic cyclins in G2 to allow into M phase.
Progression through fission yeast cell cycle requires phosphorylation-dephosphorylation of critical cdc2 residues.
CAK
Phosphorylates cdc2 on Threonine161 in G2.
Wee 1
Phosphorylates cdc2 on tyrosine15 in G2. Without it, the cell will go thru G2 quickly and the cell that hasn’t grown to the sufficient size will divide and yield in two smaller cells named wee cells.
Tyrosine 15
It’s phosphorylation inhibits action of threonine161 phosphorylation
Threonine 161
Its phosphorylation is required for yeast cell to undergo mitosis. Its activity is inhibited by Tyr15 phosphorylation
Cdc25
If everything is fine within the yeast cell, This phosphotase acts on Tyr15 to erase the phosphorylation. Without cdc25, cells will grow but will not go thru mitosis.
Controlled proteolysis
Ubiquitin-proteasome system. It regulates concentrations of cyclins and other key cell cycle proteins by adjusting the rate of synthesis and rate of destruction of the molecules at different points in cell cycle.
Subcellular localization
Dynamic phenomenon in which cell cycle regulators are moved into different compartments at different stages. Ex: cyclin B1 shuttles between nucleus and cytoplasm until G2, when it accumulates in the nucleus just prior to onset of mitosis. Cyclin B1 has a nuclear localization sequence that is phosphorylated and blocks the export of it from the nucleus.
Combinations of cyclins and Cdks at different stages in mammalian cell cycle
Cdk4/6 + cyclin D = G1
Cdk2 + cyclin E = entry into S
Cdk2 + cyclin A = through S phase
Cdk1 + cyclin B/A = MPF
Cdk inhibitors
p27, inhibitor of cyclin A-Cdk2, and must be degraded before entry into S.
Prophase
Chromosomes form - protein scaffold gives the shape of the chromosome Cytoskeleton disassembles Mitotic spindle forms Nuclear membrane dissolves ER/Golgi fragment.
Cohesin
Holds sister chromatids together. It is dissociated by phosphorylation during prophase except for at the centromere where it is unphosphorylated.
Condensin
Multi protein complex that is responsible for compaction. It replaces cohesin in prophase by dissociating cohesin with polo-like kinase (PLk) and Aurora B kinase
Centromere
Highly repeated DNA sequences allow specific protein binding.
Kinetochore
Sits atop the centromere, has 100+ proteins.
Attachment to microtubules of mitotic spindle
Home to motor proteins for chromosome mobility
Mitotic checkpoint signaling component site.
Plus end of microtubules are adjacent to it.
Mitotic spindle
Replicated during S phase.
During mitosis, they separate into two so each cell gets 2 centrioles.
Mammary cancer cells can contain multiple centrosomes.
Prometaphase
Marked by:
Mitotic spindle fully assembled
Sister chromatids line-up at center
Metaphase
Loss and addition of subunits is a dynamic process at the kinetochore
Sister chromatids are ready to separate
Anaphase
Pulling apart happens
Anaphase A: sister chromatids pull apart
Anaphase B: mitotic spindles pull apart
Spindle assembly checkpoint (SAC)
Needed to go to Anaphase
Assures metaphase plate
Activation induces delay of anaphase entry
Anaphase promoting complex (APC)
Along with SCF complex, ubiquitinate substrates, leading to their destruction by proteasomes.
APC(Cdc20)
Targets anaphase inhibitor securin (secures attachment of sister chromatids ).
APC(Cdh-1)
Targets mitotic cyclins near the end of Mitosis, targets cyclin B (part of MPF).
Telophase
Daughter cells start to return to interphase
Abscission
Mammalian cells undergoing the final stage in cytokinesis.
Midbody
What’s left of the mitotic spindle central body of the mother cell in between the two newly formed cell.
Cytokinesis
Breaking of two daughter cells.
Actin filament ring interspersed with bipolar myosin filament forms and the ring contracts and forms cleavage furrow then it pinches off the daughter cells.
