Tumor suppressors — The TP53 gene on chromosome 17 encodes a protein with which primary cellular role?

Introduction:
TP53 encodes the p53 protein, one of the most studied tumor suppressors. This question tests recognition of its central role in protecting cells from malignant transformation.

Given Data / Assumptions:

• p53 responds to DNA damage, oncogene activation, and stress.
• Chromosome location: human chromosome 17p13.
• Tumor suppressor function limits proliferation of damaged cells.

Concept / Approach:
p53 acts as a transcription factor that controls genes governing cell cycle arrest (e.g., p21), DNA repair, senescence, and apoptosis. Loss or mutation of TP53 removes these checkpoints, enabling accumulation of mutations and cancer progression.

Step-by-Step Solution:

Verification / Alternative check:
High mutation frequency of TP53 across cancers and its downstream targets (e.g., p21) confirm this regulatory role in genome surveillance.

Why Other Options Are Wrong:

• Digestive enzyme: unrelated to nuclear checkpoint control.
• Glucose transporter: that is GLUT family, not TP53.
• White blood cell receptor: p53 is ubiquitous, not lineage specific.
• Mitochondrial ATP synthase: encoded by distinct nuclear/mtDNA genes.

Common Pitfalls:
Confusing oncogenes (gain-of-function drivers) with tumor suppressors (loss-of-function guardians). TP53 is the latter.

Final Answer:
A regulator of the cell cycle and genome integrity.