Orphan CpG islands as alternative promoters.

Abstract

CpG islands (CGIs) are associated with ∼60% of mammalian promoters. Most unmethylated CGIs exhibit transcriptional activity, which has led to their co-option as promoters by retrogenes. CGIs may also serve as alternative promoters for downstream genes with methylated promoters, with implications on aberrant activation of oncogenes in cancer phenotypes.