Regulation of Mitosis in cell cycle division.pptx

In regulation of mitosis involved only cyclin B & CDK 1

1. Regulation of Mitosis Tanvi Raulaji Department of Biosciences, Bakrol

2. Introduction to Mitosis Equational Division 1]Prophase 2]Metaphase 3]Anaphase 4]Telophase 5]Cytokinesis

3. Regulatory Mechanisms

4. Control of mitosis by M Cdk

5. Mechanism of CDK Phosphatase enzyme

6. Role of cyclin B & CDK1 Act as master regulator of mitosis It activates process like nuclear envelope breakdown . chromosome condensation . . . spindle assembly . . . anaphase initiation

7. Spindle Assembly checkpoint It’s control mechanism that ensure all chromosomes are properly attached to the mitotic spindle before cell division. it prevent errors in chromosome segregation. The Spindle Assembly Checkpoint (SAC) is a critical regulatory mechanism in eukaryotic cell division (mitosis) that ensures proper chromosome segregation. Its primary function is to prevent the premature separation of sister chromatids by delaying the progression of mitosis until all chromosomes are properly attached to the spindle apparatus via kinetochores. Here’s how SAC works in a simplified way: Chromosome Alignment : During metaphase, the chromosomes must align at the metaphase plate with their kinetochores attached to spindle microtubules from opposite poles. 2. SAC Activation : If any chromosome is not properly attached or aligned, the SAC becomes active. It does this by generating a "wait" signal that prevents the anaphase-promoting complex/ cyclosome (APC/C) from being activated

8. . 3. Inhibition of APC/C : The APC/C is responsible for initiating anaphase by marking specific proteins like securin for degradation, leading to the activation of separase , which then cleaves cohesin and allows sister chromatids to separate. When the SAC is active, it inhibits the activation of APC/C, ensuring that anaphase is not initiated prematurely. 4. Checkpoint Satisfaction : Once all chromosomes are properly attached and aligned, the SAC is satisfied. This leads to the release of the inhibition on APC/C, allowing cell division to proceed into anaphase and eventually cytokinesis Key Proteins Involved : Mad1, Mad2, Bub1, BubR1: These proteins are part of the SAC signaling pathway. Mad2, for instance, binds to Cdc20 (a co-activator of APC/C), preventing APC/C from activating until proper attachment is achieved.Mps1: This kinase is important for the recruitment and activation of SAC proteins at the kinetochores. Aurora B kinase : It monitors tension at the kinetochore-microtubule attachments and helps to destabilize improper attachments. The SAC is vital for maintaining genomic stability. Failures in SAC function can lead to aneuploidy, where cells inherit the wrong number of chromosomes, contributing to cancer and other diseases.

9. Due to Errors in mitosis Cancer Chromosomal instability Aneuploidy This regulation in mitosis is importance because for healthy cell division.

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