Background:Dioxygenase that mediates demethylation of DNA and RNA containing 1-methyladenosine(m1A)(PubMed:12486230, PubMed:12594517, PubMed:16174769, PubMed:26863196, PubMed:26863410). Repairs alkylated DNA containing 1-methyladenosine(m1A) and 3-methylcytosine(m3C) by oxidative demethylation(PubMed:12486230, PubMed:12594517, PubMed:16174769). Has a strong preference for single-stranded DNA(PubMed:12486230, PubMed:12594517, PubMed:16174769). Able to process alkylated m3C within double-stranded regions via its interaction with ASCC3, which promotes DNA unwinding to generate single-stranded substrate needed for ALKBH3(PubMed:22055184). Also acts on RNA(PubMed:12594517, PubMed:16174769, PubMed:26863196, PubMed:26863410, PubMed:16858410). Demethylates N(1)-methyladenosine(m1A) RNA, an epigenetic internal modification of messenger RNAs(mRNAs) highly enriched within 5'-untranslated regions(UTRs) and in the vicinity of start codons(PubMed:26863196, PubMed:26863410). Requires molecular oxygen, alpha-ketoglutarate and iron(PubMed:22055184, PubMed:16858410).