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Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA
¹ Departments of Medicine and of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA

(Requests for offprints should be addressed to S E Diamond, Department of Physiology, University of Kentucky College of Medicine, 800 Rose Street, Lexington, KY 40536-0298; Email: sediam0{at}uky.edu)

(C J Hoon is now at Martek Biosciences Corporation, 4909 Nautilus Court North, #208, Boulder, Colorado 80301, USA)

Many transcription factors are expressed as multiple isoforms with distinct effects on the regulation of gene expression, and the functional consequences of structural differences between transcription factor isoforms may allow for precise control of gene expression. The pituitary transcription factor isoforms Pit-1 and Pit-1ß differentially regulate anterior pituitary hormone gene expression. Pit-1 is required for the development of and appropriate hormone expression by anterior pituitary somatotrophs and lactotrophs. Pit-1ß differs structurally from Pit-1 by the splice-insertion of the 26-residue ß-domain in the trans-activation domain, and it differs functionally from Pit-1 in that it represses expression of the prolactin promoter in a cell-type specific manner. In order to identify signal and promoter context requirements for repression by Pit-1ß, we examined its function in the presence of physiological regulatory signals as well as wild-type and mutant Pit-1-dependent target promoters. Here, we demonstrate that Pit-1ß impairs recruitment of cAMP response element-binding protein (CREB)-binding protein to the promoters that it represses. In addition, we show that repression of target promoter activity, reduction in promoter histone acetylation, and decrease of CREB-binding protein recruitment all depend on promoter context. These findings provide a mechanism for promoter-specific repression by Pit-1ß.

This article has been cited by other articles:

				D. L. Duval, M. D. Jonsen, S. E. Diamond, P. Murapa, A. Jean, and A. Gutierrez-Hartmann Differential Utilization of Transcription Activation Subdomains by Distinct Coactivators Regulates Pit-1 Basal and Ras Responsiveness Mol. Endocrinol., January 1, 2007; 21(1): 172 - 185. [Abstract] [Full Text] [PDF]

				R A Sporici, J S Hodskins, D M Locasto, L B Meszaros, A L Ferry, A M Weidner, C A Rinehart, J C Bailey, I M Mains, and S E Diamond Repression of the prolactin promoter: a functional consequence of the heterodimerization between Pit-1 and Pit-1 {beta} J. Mol. Endocrinol., October 1, 2005; 35(2): 317 - 331. [Abstract] [Full Text] [PDF]