3'-UTR involving regulation by miRNA (Section of mRNA following stop codon, Contains elements reg. expression post-translationally, Binds reg. proteins + miRNA, miRNA binding = reduce gene expression → inhibit translation/mRNA cleavage, Effect on SULT1A1 activity (Decr. enzyme activity in homo/heterozygotes for T allele, C973T = 3'end of UTR, More effective miRNA-631 binding = more down-regulation of expression — confirmed with reporter gene assay, 20% white US pop. homozygous)