Telophase in Cell Division
Concept Map
Telophase is the final stage of cell division in eukaryotic cells, crucial for the proper segregation of chromosomes and the re-establishment of cellular structures. It involves the decondensation of chromosomes, reassembly of the nuclear envelope, and disassembly of the mitotic spindle. Molecular mechanisms like the dephosphorylation of proteins by phosphatases, such as Cdc14 in yeast, and the degradation of cyclins by the APC/C are key for transitioning from mitosis to cytokinesis. Additional regulatory proteins like Cdc48/p97 also play a significant role in telophase progression.
Summary
Outline
Understanding Telophase in Cell Division
Telophase represents the concluding phase of cell division in eukaryotic cells, completing the processes of mitosis and meiosis. It is characterized by the re-establishment of the cell's normal structures after the chromosomal separation of earlier stages. Chromosomes, having been segregated to opposite poles of the cell, begin to decondense into chromatin. The nuclear envelope reassembles around each set of chromosomes, and nucleoli re-form within the new nuclei. The mitotic spindle, composed of microtubules that played a crucial role in chromosome separation, is disassembled, with its components being recycled for future use. Telophase is a short but critical phase, occupying approximately 2% of the cell cycle's duration, and sets the stage for the subsequent process of cytokinesis.The Transition from Telophase to Cytokinesis
Cytokinesis is the division of the cytoplasm that results in the formation of two distinct daughter cells, and it often initiates while telophase is still underway. The coordination between telophase and cytokinesis ensures that each daughter cell receives an equal and complete set of genetic material along with the necessary cellular organelles. This transition is essential for the maintenance of genetic stability and cell function, as it culminates the process of cell division by physically separating the two daughter nuclei into individual cells.Molecular Mechanisms Regulating Telophase
The orderly progression through telophase is governed by complex molecular mechanisms, including the dephosphorylation of proteins previously phosphorylated by mitotic cyclin-dependent kinases (Cdks). The phosphorylation of these substrates by M-Cdks is crucial for initiating mitotic events such as spindle formation, chromosome condensation, and nuclear envelope breakdown. The subsequent dephosphorylation signals the disassembly of the spindle, the decondensation of chromosomes, and the reformation of the nuclear envelope. The transition from phosphorylation to dephosphorylation is facilitated by the inactivation of Cdks through the proteolytic degradation of their cyclin partners by the anaphase-promoting complex/cyclosome (APC/C), a ubiquitin ligase. This degradation, commencing in anaphase, is vital for the cell's progression into telophase.The Role of Phosphatases in Telophase
Phosphatases are crucial in telophase as they reverse the phosphorylation of Cdk substrates, enabling the cell to exit mitosis. In the model organism Saccharomyces cerevisiae, or budding yeast, the phosphatase Cdc14 is essential for this transition. Inhibition of Cdc14 activation results in a cell cycle arrest similar to that caused by the failure to degrade M-cyclins, highlighting the importance of phosphatase activity in conjunction with cyclin degradation for successful cell cycle progression through telophase.Reconsidering the Passive Nature of Anaphase and Telophase
Anaphase and telophase were once considered passive phases that occurred after the spindle-assembly checkpoint was satisfied, allowing the transition from metaphase to anaphase. However, emerging research indicates that these phases may involve additional, active checkpoints. For example, the regulation of Cdc14 phosphatase activity differs between anaphase and telophase, suggesting more sophisticated control mechanisms. Cdc14 is released from the nucleolus and exported to the cytoplasm, with its full release and sustained activity being essential for the disassembly of the spindle apparatus and the reassembly of the nuclear envelope.Additional Mechanisms Driving Telophase
In addition to the shift in phosphorylation states, a variety of regulatory mechanisms contribute to the initiation of telophase. The physical separation of chromosomes from the metaphase plate during anaphase may provide cues for the onset of telophase. Proteins such as Cdc48 in yeast (and its human homolog, p97) are also critical for the progression of telophase. These proteins use ATPase activity to change the conformation of other proteins, aiding in spindle disassembly, nuclear envelope reformation, and chromosome decondensation. Cdc48/p97 also targets certain ubiquitinated proteins for proteasomal degradation, further illustrating the complex regulation of telophase.
Show More
Understanding Telophase
Definition of Telophase
Telophase is the final phase of cell division in eukaryotic cells, where the cell's normal structures are re-established after chromosomal separation
Characteristics of Telophase
Chromosome Decondensation
During telophase, chromosomes begin to decondense into chromatin
Nuclear Envelope Reassembly
The nuclear envelope reforms around each set of chromosomes during telophase
Mitotic Spindle Disassembly
The mitotic spindle, composed of microtubules, is disassembled during telophase
Role of Telophase in Cell Cycle
Telophase is a short but critical phase that sets the stage for the subsequent process of cytokinesis
Transition from Telophase to Cytokinesis
Definition of Cytokinesis
Cytokinesis is the division of the cytoplasm that results in the formation of two distinct daughter cells
Coordination between Telophase and Cytokinesis
The coordination between telophase and cytokinesis ensures that each daughter cell receives an equal and complete set of genetic material and cellular organelles
Molecular Mechanisms Regulating Telophase
Role of Phosphorylation and Dephosphorylation
The orderly progression through telophase is governed by the phosphorylation and dephosphorylation of proteins, including those phosphorylated by mitotic cyclin-dependent kinases
Inactivation of Cdks through APC/C
The anaphase-promoting complex/cyclosome (APC/C) plays a crucial role in the transition from phosphorylation to dephosphorylation by degrading cyclin partners of Cdks
Role of Phosphatases in Telophase
Phosphatases, such as Cdc14 in budding yeast, are essential for reversing the phosphorylation of Cdk substrates and allowing the cell to exit mitosis
Additional Mechanisms Driving Telophase
Physical Separation of Chromosomes during Anaphase
The physical separation of chromosomes from the metaphase plate during anaphase may provide cues for the onset of telophase
Role of Proteins such as Cdc48
Proteins like Cdc48 in yeast play a critical role in spindle disassembly, nuclear envelope reformation, and chromosome decondensation during telophase
Telophase in Cell Division
Learn with Algor Education flashcards
Click on each Card to learn more about the topic
00
During telophase, chromosomes that were previously separated start to transform back into ______.
chromatin
01
The ______ envelope reforms around each group of chromosomes, signaling the end of telophase.
nuclear
02
The mitotic ______, essential for chromosome separation, is broken down and its parts are saved for later use.
spindle
