A 72-Base Pair AT-rich DNA Sequence Element Functions as a Bacterial Gene Silencer

Chien Chung Chen, Ming Fang, Arundhati Majumder, Hai Young Wu*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

26 Scopus citations


We have previously demonstrated that sequential activation of the bacterial ilvIH-leu O-leuABCD gene cluster involves a promoter-relay mechanism. In the current study, we show that the final activation of the leuABCD operon is through a transcriptional derepression mechanism. The leuABCD operon is transcriptionally repressed by the presence of a 318-base pair AT-rich up-stream element. LeuO is required for derepressing the repressed leuABCD operon. Deletion analysis of the repressive effect of the 318-bp element has led to the identification of a 72-bp AT-rich (78% A+T) DNA sequence element, AT4, which is capable of silencing a number of unrelated promoters in addition to the leuABCD promoter. AT4-mediated gene silencing is orientation-independent and occurs within a distance of 300 base pairs. Furthermore, an increased gene-silencing effect was observed with a tandemly repeated AT4 dimer. The possible mechanism of AT4-mediated gene silencing in bacteria is discussed.

Original languageEnglish
Pages (from-to)9478-9485
Number of pages8
JournalJournal of Biological Chemistry
Issue number12
StatePublished - 23 03 2001


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