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#APC

5 public questions tagged with this topic.

Cell Cycle Regulation

Which protein is degraded by APC to trigger chromosome separation?

Chromatid cohesion must be maintained until synchronous separation at anaphase, requiring protection against premature cleavage. Securin, also called pituitary tumor transforming gene PTTG, functions as dual inhibitor and chaperone of separase. Securin sequence contains D-box and KEN motifs for APC/C recognition and binds separase HEAT repeats, occluding catalytic triad. Accumulation during S and G2 concentrates at centromeres. At metaphase, APC/C-Cdc20 polyubiquitinates securin, triggering rapid proteasomal degradation within five to ten minutes, concentration dropping precipitously. Simultan

Ref: Uhlmann et al., Nature 1999, Separase Cohesin Cleavage. Alberts 7th ed., Chapter 17, Securin.

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Cancer

Sequential mutations in APC, KRAS, SMAD4 and TP53 illustrate

The tumor-suppressor protein p53 is kept at low levels in unstressed cells by continuous MDM2-mediated ubiquitination and degradation. DNA damage or oncogenic stress leads to phosphorylation of p53 or induction of ARF, both of which block the p53–MDM2 interaction. Stabilized p53 then transcriptionally activates genes that induce cell-cycle arrest, DNA repair or apoptosis, thereby preventing propagation of damaged genomes.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Loss of APC function primarily affects which signaling pathway?

Wnt/β-catenin, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling Dev Bio & Other Pathways

APC and Axin function as

Scaffold proteins, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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