How are genes affected by promoter cpg island methylation in aging?

Answer 1

In Cancer (a disease of aging) some cpg islands are hyper-methylated even though the entire genome is hypo-methylated. This paradoxical hyper- and hypo-methylation contributes to loss of function of tumor suppressor genes (by hyper-methylation) and gain of function of proto-oncogenes by hypo-methylation (turning them into oncogenes).

Methylation of a promoter region is one mechanism that can regulate expression of the associated gene. When the promoter is methylated transcription is blocked. Hypo-methylation results in over-expression of the gene. Hypermethylation leads to under-expression of the gene. The cell's environment, the body's nutritional status, and early 'genomic imprinting' (a process that occurs shortly after conception) can change methylation status of promoter regions.

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