416 Biotechnology Building
Barbara McClintock Professor of Molecular Biology & Genetics
John Lis is a Professor in the Department of Molecular Biology and Genetics. He did his graduate research at Brandeis University and received his Ph.D. in Biochemistry in 1975. His postdoctoral work focused on Drosophila gene regulation and chromosome structure at Stanford University, during which time he was supported by a fellowship from the Helen Hay Whitney Foundation. Dr. Lis joined the faculty at Cornell in 1978. His research program has been supported by the National Institutes of Health, including a MERIT Award, March of Dimes, American Cancer Society, Cornell Biotechnology Institute, and a Proctor and Gamble University Exploratory Research Grant.
The regulated production of a mature mRNA in eukaryotes requires highly coordinated molecular interactions and biochemical processes that involve the participation of hundreds of proteins. Our lab is focusing on the molecular mechanisms that govern the regulated transcription and processing of these mRNAs using as a primary model system the highly-inducible heat shock (HS) genes. Over the past 2.5 decades, our laboratory has applied, and in some cases developed, strategies such as protein/DNA crosslinking, DNA footprinting, and transgenics to probe the structure of promoters and genes and their activities in living cells [Lis (1998)]. We are continuing to use both well-established and new technologies to identify protein factors that participate in the HS gene mRNA production, and to define with high temporal and spatial resolution in vivo protein/nucleic acid and protein/protein interactions during the process of gene activation.
The second stage of our analysis is to deplete or inactivate specific transcription factors or particular surfaces of these factors in vivo and then to reexamine the consequences on HS promoters and genes.
Our past studies have shown (Guzman and Lis, 1999) that a rapidly-acting conditional mutant can be an invaluable tool in assessing the mechanistic role of a particular transcription factor in vivo. We are using a variety of fast-acting conditional mutants that encode Drosophila proteins that we hypothesize are critical for both establishing the potentiated promoter and for its activation. We are assessing the roles of these proteins in regulating chromatin architecture and function of the heat shock promoter (using the methods described above) in the seconds or minutes following the conditional disruption of a particular protein. Likewise, drugs that rapidly inhibit particular active sites of proteins believed critical for transcription and its regulation are also being used to evaluate the primary functions of these proteins in regulating chromatin architecture and function of the heat shock promoter (Ni et al. 2004)
While fast-acting conditional mutations provide an established means of evaluating a protein's role in a biological mechanism in vivo, inhibitors that bind particular protein surfaces could provide a much finer dissection. We are selecting RNA aptamers that bind to a specific protein surface and inhibit its function. These RNA aptamers are produced by cycles of selection and amplification from large RNA pools (our latest contains 1016 RNA molecules that have a random 50-mer in their centers) to isolate small RNA molecules that bind to specific protein components. Our goal is to overproduce selected RNAs in cells or in an organism to provide a way of inactivating specific protein domains and thereby assess their function and mechanism of action in vivo. These aptamers provide several advantages as specific inhibitors, including (i) like an antibody, they can be made to order specifically for a particular protein, (ii) like a small organic molecule, they are able to rapidly target a specific protein domain within cells, and (iii) like a conditional allele, they are able to exert their effect in whole organisms, but (iv) also are targetable to specific tissues, cells, or stages of development. We have succeeded in selecting RNAs that bind tightly to a specific protein in vitro, and have demonstrated their effect in vivo (Shi et al., 1999). We are currently selecting RNAs designed to interfere with specific steps in transcription and its control (Fan et al. 2004).
Click here to view Dr. Lis' PubMed listings.