MicroRNA-21-3p, a berberine-induced miRNA, directly down-regulates human methionine adenosyltransferases 2A and 2B and inhibits hepatoma cell growth.

Methionine adenosyltransferase (MAT) is the cellular enzyme that catalyzes the synthesis of S-adenosylmethionine (SAM), the principal biological methyl donor and a key regulator of hepatocyte proliferation, death and differentiation. Two genes, MAT1A and MAT2A, encode 2 distinct catalytic MAT isoforms. A third gene, MAT2B, encodes a MAT2A regulatory subunit.