Developmentally-regulated interaction of a transcription factor complex containing CDP/cut with the early histone H3 gene promoter of the sea urchin Tetrapygus niger is associated with changes in chromatin structure and geneexpression

During sea urchin embryogenesis the early historic genes are temporally exp ressed to accommodate the high demand for historic proteins during DNA repl ication at early cleavage stages of development. The early histone genes ar e transcriptionally active from the 16-cell stage, reaching a peak in expre ssion at the 128-cell stage that gradually decreases until expression is co mpletely inhibited at the late blastula stage. We are studying the gene reg ulatory mechanisms that control early historic gene expression in sea urchi ns to understand the interrelationships between chromatin remodeling and tr anscriptional activation during development. Here, we have investigated chr omatin organization and transcription factor interactions by analyzing nucl ease hypersensitivity and protein binding in the promoter region of the ear ly historic H3 gene from the sea urchin Tetrapygus niger. We have found a D Nase I hypersensitive domain centered at -90 in the early historic H3 gene promoter which is only detected in embryos at the 128-cell stage expressing high levels of early histone H3 mRNA. This hypersensitive site (-110 to -7 0) encompasses two regulatory elements (TnH3NFH3.1 and TnH3CCAAT). The -94 to -77 region of the historic H3 promoter is recognized by a transcription factor complex in nuclear extracts from 128-cell embryos. Methylation inter ference analysis and competition studies demonstrated a specific interactio n at the CCAAT sequence. Using specific antibodies we find that the homeodo main transcription factor CDP/cut is the DNA-binding component of the compl ex interacting with the early historic H3 gene promoter in T. niger. Our re sults provide further evidence for the functional role of CDP/cut in develo pmental regulation of histone gene expression in phylogenetically diverse e ukaryotic species. (C) 2001 Elsevier Science B.V. All rights reserved.