The transcriptional and chromatin profile of the promoter, first exon and first intron of the human TH gene were analyzed in human neuroblastoma BE(2)-C-16 and human renal carcinoma 293FT cell lines. The latter is a cell culture system that is not permissive for TH gene expression, whereas the former has a 50% cell fraction that tests positive for TH. The engineering of a 6.3 kb recombinant human TH promoter revealed the presence of repressors of transcription between positions (−6,244/ −194). The addition of a 1.2 kb fragment of the first intron of the human TH gene (+730/+1,653) enhanced transcriptional activity of the recombinant promoter. However, both constructs were not specific for TH-positive BE(2)-C-16 cells. Chromatin immunoprecipitation (Chip) analysis was carried out on BE(2)-C-16 and 293FT cells to probe sequences of promoter, first exon and first intron of the human TH gene from position (−448/+1,204). The presence of nucleosomes was observed approximately from position (−20/+473) in both cell lines. Chip analysis was then conducted to determine the acetylation of various lysine residues of H3 and H4 in both cell lines. All analyzed lysine residues of H3 and H4 were acetylated in BE(2)-C-16 cells, whereas 293FT cells tested positive for acetylation only in the external lysine residues of the histone tail. Our data are compatible with an active TH gene expression in a 50% cell fraction of BE(2)-C-16 cells. Further analysis of epigenetic programming might lead to the identification of the factors that determine TH gene expression specifically in dopaminergic neurons.The elucidation of the mechanism of human tyrosine hydroxylase (TH) gene regulation is one of the key issues in the field of neurology. The function of TH consists of catalyzing tyrosine hydroxylation in the synthesis of L-dopa (Nagatsu et al., 1964), which is the rate-limiting step in the generation of catecholamine neurotransmitters of the central and peripheral nervous systems (Zigmond et al., 1989). There are a number of important reasons to continue to explore the complex mechanism of TH gene regulation. For instance, aberrant TH gene expression is observed in alcoholism and in psychiatric illnesses, such as schizophrenia and bipolar disorder (Ishiguro et al., 1998). In addition, the degeneration of TH-positive dopaminergic neurons of the substantia nigra is associated with Parkinson's disease (Moore, 2003).Many studies have been conducted to characterize the factors that come into play in TH gene regulation. These studies focused mainly on the human (Kessler et al., 2003;Romano et al., 2005;Jin et al., 2006), mouse (Kim et al., 2003a) and rat models (Gandelman et al., 1990 et al., 2003b). In a previous report, a 13 kb DNA fragment containing the human TH promoter was isolated from a genomic DNA library, sequenced and utilized to generate both a transgenic animal model (Kessler et al., 2003) and a variety of recombinant minimal TH promoters assembled in a self-inactivating lentiviral vector system (Romano et al., 2005). All...