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Professor and Chair John Anagli, PhD Adjunct Assoc. Prof Rodrigo Andrade, Ph.D. Professor Jacob Aranda, MD, PhD Prof. Pediatrics, Pharm Cristina Artalejo, MD, PhD Assoc. Professor Michael Bannon, PhD Professor Julie Boerner, PhD Asst Prof. KCI, Pharm Chaya Brodie, PhD Adjunct Professor Dharam Chopra, PhD Prof. IEHS, Pharm Nicholas Davis, PhD Assoc. Prof. Gregory Kapatos Professor David Kessel, PhD Professor Thomas Kocarek, PhD Assoc. Prof. IEHS, Pharm Lawrence Lash, PhD Professor Karin List, PhD Asst. Prof Larry Matherly, PhD Professor Raymond Mattingly, PhD Assoc. Prof. Roy B. (Mac) McCauley, PhD Professor Kamiar Moin, PhD Subsidy Assoc.Prof. Raymond Novak, PhD Director IEHS, Pharm John Reiners, Jr., PhD Prof., IEHS, Pharm Sandra Rempel, PhD Adjunct Assoc Prof Tiziano Scarabelli, MD.PhD Adjunct Assoc Prof. David Schneider, PhD Assoc. Prof. Eugene Schoener, PhD Professor Robert B. Silver, PhD Prof. Pharm, Physiol, Radiol. Manuel Tancer, MD Prof. Psychiatry, Pharm Stanley Terlecky, PhD Assoc. Prof. Ellen Tisdale, PhD Assoc. Prof. Arun Wakade, PhD Professor Hai-Young Wu, PhD Assoc. Prof. Akio Yamazaki, PhD Prof. Ophthal., Pharm Russell Yamazaki, PhD Assoc. Prof, Assoc. Chair
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 Hai-Young Wu, Ph.D. Associate Professor of Pharmacology Department of Pharmacology, Wayne State University, School of Medicine, 540 E. Canfield, Detroit MI 48201 Tel: (313) 577-1584 FAX: (313) 577-6739 E-mail: haiwu@med.wayne.edu Research interest: Genome Organization: DNA Supercoiling and Transcription Control Disorders of gene expression regulation underlie human diseases. The torsional stress placed upon DNA is integral to the regulation of gene expression, yet the mechanisms involved in these DNA supercoiling effects remain elusive. The fact that transcriptional elongation itself generates superhelical tension on the DNA has further complicated the issue. Nonetheless, the fundamental effects of changes in DNA structure on gene expression are common to all organisms. In our studies on the role of DNA supercoiling in the leu-500 activation phenomenon in Salmonella typhimurium topA mutants, we found a control mechanism, the promoter relay mechanism, which coordinates the expression of genes in the ilvIH-leuO-leuABCD gene cluster. Transcription-driven DNA supercoiling plays a decisive role in the mechanism. Two cis-elements important for the gene expression regulation have been identified. It is the structure of, rather than the specific sequences of these DNA elements that are important for transcriptional regulation. These findings have led to our hypothesis that transcription-driven DNA supercoiling serves as a signal in transcriptional control via modulating DNA geometry and thus the functions of the cis-elements. Further, the responsiveness of the functions of these cis-elements to the activities of adjacent transcriptional units enables these elements to coordinate the expression of a group of genes in a sequential manner. The identified cis-elements are the gene silencer AT8 and the LeuO-binding site AT7. We have recently demonstrated that a cis-spreading histone-like nucleoid structuring protein (H-NS)-associated nucleoprotein filament is responsible for AT8-mediated gene silencing, and AT8, in fact, is a nucleation site for recruiting H-NS to form a proximal nucleoprotein filament, which is transcriptionally repressive for the regional genes. The silencing activity is gene non-specific and can extend up to 400 bp, which is considered a long distance in the bacterial genome. The second cis-element important for the transcriptional regulation is a 25-bp LeuO-binding site, AT7, which is located adjacent to AT8 The binding of the trans-acting LeuO to AT7 is required for the relief of AT8-mediated gene silencing. LeuO appears to relieve gene silencing via a boundary element-like activity, which blocks the cis-spreading pathway of the H-NS-associated nucleoprotein filament. While LeuO is capable of blocking gene-silencing activity from reaching the target promoter, LeuO itself is a transcriptionally inert element. Such boundary element activity is unprecedented in bacterial transcriptional regulation, however, is basically consistent with the barrier function of the eukaryotic boundary elements/insulators. This provides an excellent model system for elucidating the interplay between transcription-driven DNA supercoiling and the chromosomal barriers for their roles in transcriptional regulation. Data suggested that LeuO delimits the transcriptionally active and repressive domains on the bacterial chromosome via a hypothetical genome-wide LeuO-LeuO interaction network. The proposed chromosome-wide sequestrations result in topologically isolated domains that may modulate the chromosomal DNA supercoiling dynamics and thus gene expression. Hence, the elucidated mechanistic details of the boundary element activity of LeuO will shed light on the currently ill-defined effects of transcription-driven DNA supercoiling on the expression of many genes, including human c-myc and BRCA1, that involve DNA structural transitions in their regulation. Our research effort is likely to establish a causal relationship of DNA supercoiling-structural transition-function, which will provide valuable information for the advance of this emergent research field and lead to new therapeutic strategies for the treatments of pertinent human diseases. Additional information is available at the website of Dr. Wu’s laboratory at http://146.9.23.173/
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