Open Accesscis -Acting Site Controlling Bidirectional Transcription at the Growth-Differentiation Transition in Dictyostelium discoideum
Author(s) -
Shigenori Hirose,
Samuel H. Payne,
William F. Loomis
Publication year - 2006
Publication title -
eukaryotic cell
Language(s) - English
Resource type - Journals
eISSN - 1535-9778
pISSN - 1535-9786
DOI - 10.1128/ec.00047-06
Subject(s) - biology , transcription (linguistics) , dictyostelium discoideum , transcription factor , psychological repression , dictyostelium , genetics , cis regulatory module , gene , microbiology and biotechnology , gene expression , promoter , philosophy , linguistics
A pair of adjacent genes,impA anddia1 , are divergently transcribed but expressed at different stages in the life cycle ofDictyostelium discoideum . The intervening 654-bp region carriescis -acting regions that are essential for transcription in both directions as well as repression ofdia1 in growing cells. We have focused on a 112-bp region proximal todia1 that is essential for bidirectional transcription. Analyses of a set of internal deletions showed that the sequence between positions 80 and 97 (TTTGAAGAATTT) is critical and that bases outside this region are dispensable. Site-directed mutations within this critical region confirmed the importance of this sequence for transcription both to the right and to the left. However, insertions of either 6 or 24 Ts into the run of 6 Ts separating the repeated GAA sequence had little effect on the functioning of the site in either direction, suggesting that factors recognize the half-sites TTGAATT separately. Inversion of the bases between positions 80 and 97 greatly reduced expression in both directions, indicating that orientation is critical for expression of both the nearbyimpA gene and the distaldia1 gene, which is more than 500 bp away. Comparison of 38 mutant constructs with multiple random variations in the region indicated that transcription factors may bind to a range of related sequences and still retain function. All functional constructs directed transcription both leftward and rightward, while all nonfunctional constructs were impaired for transcription in both directions. It appears that the same transcription complex controls transcription of bothimpA anddia1 .