Epigenetic silencing of tumor suppressor genes through promoter CpG island hypermethylation is a key mechanism in carcinogenesis. The enzyme catalyzing addition of methyl groups to cytosine residues in CpG dinucleotides is:

• A DNA methyltransferase (DNMT) ✓
• B Histone deacetylase (HDAC)
• C Ten-eleven translocation (TET) dioxygenase
• D EZH2 (enhancer of zeste homolog 2)

Explanation

DNA methyltransferases (DNMT1, DNMT3A, DNMT3B) catalyze transfer of a methyl group from S-adenosylmethionine to the 5-position of cytosine in CpG dinucleotides. Hypermethylation of gene promoter CpG islands silences expression, equivalent to a 'hit' on a tumor suppressor. HDAC removes acetyl groups from histones, compacting chromatin; TET enzymes oxidize 5-methylcytosine toward demethylation; EZH2 is a histone methyltransferase (H3K27me3) involved in Polycomb-mediated gene silencing.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.