The Homeodomain Protein Arix Interacts Synergistically with Cyclic AMP to Regulate Expression of Neurotransmitter Biosynthetic Genes*
- From the Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, Oregon 97201
Abstract
Transcription of the neurotransmitter biosynthetic genes tyrosine hydroxylase and dopamine β-hydroxylase (DBH) is regulated by cell type-specific transcription factors, including the homeoprotein Arix, and second messengers, including cyclic AMP. The cis-acting regulatory sites of the DBH gene which respond to Arix and cAMP lie adjacent to each other, between bases −180 and −150, in a regulatory element named DB1. Neither Arix nor cyclic AMP analogs alone effectively stimulate transcription from the DBH promoter in non-neuronal cell cultures. However, when Arix is present together with cAMP, transcription is substantially activated. Synergistic transcription from the DBH promoter can also be elicited by cotransfection of Arix with an expression vector encoding the catalytic subunit of protein kinase A. Nuclear extracts from PC12 cells display a cAMP-induced complex binding to the DB1 element, and antisera to transcription factors CREB, CREM, Fos, and Jun indicate that these proteins, or closely related family members, interact with DB1. A dominant negative construct of CREB inhibits the response of the DBH promoter to protein kinase A. These results demonstrate a synergistic interaction between a homeodomain protein and the cAMP signal transduction system and suggest that similar interactions may regulate the tissue-specific expression of neuroendocrine genes.
Footnotes
-
↵* This work was supported by National Institutes of Health Grant GM38696 (to E. J. L.) and a fellowship from the American Heart Association, Oregon Affiliate (to D. J. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵‡ To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biology, Oregon Health Sciences University, L224, Portland, OR 97201. Tel.: 503-494-5076; Fax: 503-494-8393; E-mail:lewis{at}ohsu.edu.
-
↵1 The abbreviations used are: TH, tyrosine hydroxylase; DBH, dopamine β-hydroxylase; CRE, cAMP response element; PKA, cAMP-dependent protein kinase catalytic subunit α (protein kinase A); CAT, chloramphenicol acetyltransferase; RSV, Rous sarcoma virus; CPT-cAMP, 8-(4-chlorophenylthio)adenosine 3′:5′-cyclic monophosphate; 8-Br-cAMP, 8-bromoadenosine 3′:5′-cyclic monophosphate; EMSA, electrophoretic mobility assay; HD, homeodomain; WT, wild type.
-
- Received April 7, 1997.
- Revision received July 3, 1997.
