TUBB3 expression in several human cell lines, but not in a paclitaxel-resistant cell line. RNA interference revealed that HIF1A mediated hypoxia-induced TUBB3 expression. Chromatin immunoprecipitation analysis showed that HIF1A bound an HIF1A-binding site in the 5-prime flanking region of the TUBB3 gene. Methylation of an enhancer in the 3-prime flanking region abolished hypoxia-induced TUBB3 expression. Much lower Tubb3 levels were detected in all other adult mouse tissues examined except brain, where expression was even lower. Chromatin immunoprecipitation analysis showed that HIF1A bound an HIF1A-binding site in the 5-prime flanking region of the TUBB3 gene. Methylation of an enhancer in the 3-prime flanking region abolished hypoxia-induced TUBB3 expression.