Neuronal and extraneuronal expression and regulation of the human alpha5 nicotinic receptor subunit gene.
The mRNA encoding the human alpha5 nicotinic subunit was detected in several structures of the nervous system but appeared to be mainly expressed in cerebellum, thalamus, and the autonomic ganglia. For the first time, the alpha5 transcript was also detected in several non-neuronal tissues, with maximal expressions being found throughout the gastrointestinal tract, thymus, and testis. Many other extraneuronal sites expressed alpha5, but there were also nonexpressing organs, such as the liver, spleen, and kidney. To understand the transcriptional mechanisms controlling such a diversified expression of alpha5 in neuronal and nonneuronal cells, we isolated the 5'-regulatory region of the human gene and characterized its properties. Here we identify the alpha5 core promoter and demonstrate that the DNA regions surrounding it contain elements (with positive or negative activities) that work in a tissue-specific fashion. In particular, the segment specifying the 5'-untranslated region in neuronal cells has most of the properties of an enhancer because it activates a heterologous promoter in a position- and orientation-independent fashion. We therefore conclude that the expression of alpha5 relies on a highly complex promoter that uses distinct regulatory elements to comply with the different functional and developmental requirements of the various tissues and organs.
Flora
A
A
CNR Cellular and Molecular Pharmacology Center and Department of Medical Pharmacology, University of Milan, Milano, Italy.
Schulz
R
R
Benfante
R
R
Battaglioli
E
E
Terzano
S
S
Clementi
F
F
Fornasari
D
D
D001483:Base Sequence; D002460:Cell Line; D002531:Cerebellum / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D004064:Digestive System / Q000737:chemistry; D005333:Fetus / Q000378:metabolism; D005725:Ganglia, Autonomic / Q000737:chemistry; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D011978:Receptors, Nicotinic / Q000235:genetics*; D011993:Recombinant Fusion Proteins; D013737:Testis / Q000737:chemistry; D013788:Thalamus / Q000737:chemistry; D013950:Thymus Gland / Q000737:chemistry; D020506:Untranslated Regions
D012333:RNA, Messenger; D011978:Receptors, Nicotinic; D011993:Recombinant Fusion Proteins; D020506:Untranslated Regions; D004247:DNA