Neuronal PAS Domain Protein 1 Is a Transcriptional Repressor and Requires Arylhydrocarbon Nuclear Translocator for Its Nuclear Localization

• Published in: The Journal of biological chemistry 2006-11, Vol.281 (45), p.34617-34629
• Main Authors: Teh, Christina H.L., Lam, Kevin K.Y., Loh, Chin C., Loo, Jia M., Yan, Tie, Lim, Tit Meng
• Format: Article
• Language: English
• Subjects: Animals; Aryl Hydrocarbon Receptor Nuclear Translocator - genetics; Aryl Hydrocarbon Receptor Nuclear Translocator - metabolism; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; Binding Sites; Blotting, Western; Cell Nucleus - metabolism; Cells, Cultured; Cloning, Molecular; Humans; Immunoenzyme Techniques; Immunoprecipitation; Kidney - cytology; Kidney - metabolism; Mice; Mice, Inbred C57BL; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurons - cytology; Neurons - metabolism; Plasmids - genetics; Protein Binding; Protein Transport; Receptors, Aryl Hydrocarbon; Repressor Proteins - genetics; Repressor Proteins - metabolism; Saccharomyces cerevisiae; Transcription, Genetic; Transcriptional Activation; Two-Hybrid System Techniques
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M604409200

Neuronal PAS domain protein 1 (NPAS1), a basic helix-loop-helix-PAS transcription factor expressed in the central nervous system, has been suggested to be involved in neuronal differentiation. However, relatively little is known about the molecular mechanism underlying the role of NPAS1 during development. In this study we set out to characterize the different domains within NPAS1. We showed that the nuclear localization of NPAS1 is dependent on the presence of ARNT. In addition, the transcriptional potential of ARNT is not required for this localization. In the absence of ARNT, NPAS1 is excluded from the nucleus, and this exclusion is due to the presence of a nuclear export signal within the N terminus of NPAS1. The interaction between NPAS1 and ARNT is via their N termini. We found no transactivation domain within NPAS1; instead, we mapped out at least three repression domains within NPAS1, suggesting that NPAS1 acts as a repressor. Furthermore, our experiments showed that NPAS1 is able to repress the transactivation functions of ARNT and ARNT2. We suggest that NPAS1 is guided into the nucleus by ARNT via the ARNT nuclear localization signal, and NPAS1 can override the activation function of adjacent transcription factors, providing a mechanism by which NPAS1 may inhibit transcription.