The genome of the cell is often spoken of in sacred tones and studies of genomic integrity are focused on how cells protect their genome from change. Yet, the sequencing of genomes from a wide variety of organisms demonstrates that genomes undergo continual change. This change is highlighted by the finding that some of the most abundant elements in the human genome are the genetic remnants of retroviruses and retrotransposons. Furthermore, genomic DNA is under continual mutagenic attack from both internal and external stimuli. The paradox is that such change is both fodder for oncogenic mutations that can lead to cancer and for evolutionary selection. We believe that cells have developed specific mechanisms to control the genomic change that inevitably occurs. The goal of our lab is to understand those regulatory mechanisms and to hopefully harness that understanding to manipulate the genome for experimental and therapeutic purposes.
In particular, gene targeting is the process by which an exogenous gene replaces an endogenous gene by homologous recombination. The absolute frequency of gene targeting can be increased several thousand fold by the induction of a DNA double-stranded break (DSB) in the target locus. We have found that chimeric nucleases, protein fusions between a zinc-finger DNA binding domain and the endonuclease domain from the FokI restriction enzyme, can cleave genomic DNA and stimulate gene targeting by several thousand fold. Because the zinc-finger domain can be manipulated to potentially recognize any DNA sequence, we are interested in developing chimeric nucleases as tools to stimulate gene targeting at every locus in the genome. The repair of a DSB is a regulated process and it is thought that most DSBs in mammalian cells are repaired not by homologous recombination but rather by non-homologous end-joining (NHEJ). We are interested in understanding the regulation of DSB repair by NHEJ and homologous recombination and developing tools to manipulate which way a cell repairs a DSB. By studying the regulation of DSB repair and developing chimeric nucleases as a tool to create DSBs in any sequence we hope to increase the efficiency of gene targeting so it might one day be used to treat children with genetic diseases such as sickle cell anemia.
RESEARCH INTERESTS
Homologous Recombination
Gene Targeting
Double-Strand Break Repair
Gene Therapy
Sickle Cell Disease
RECENT PUBLICATIONS
Porteus, MH, Cathomen, T, and Baltimore, D, "Efficient Gene Targeting Mediated by AAV and DNA Double-Strand Breaks" Cell Biol, 23/10:3558-3565, 2003
Porteus, MH, and Baltimore, D, "Chimeric Nucleases Stimulate Gene Targeting in Human Cells" Science 300, 763, 2003
SIGNIFICANT PUBLICATIONS
Porteus, MH, Brice AEJ, Bulfone, A, Usdin, TB, Ciaranello, RD, and Rubenstein, JLR, "Isolation and characterization of a library of cDNA clones that are preferentially expressed in the embryonic telencephalon" Mol Brain Res, 12:7-22, 1992
Porteus, MH, Bulfone, A, Ciaranello, RD, and Rubenstein, JLR, "Isolation and characterization of a novel cDNA clone encoding a homeodomain that is developmentally regulated in the ventral forebrain" Mol Brain Res, 7:221-229, 1991
Porteus, MH, Bulfone, A, Puelles, L., Liu, JK, Puelles L, Lo, L-C, and Rubenstein, JLR, "Dlx-2, Mash-1, Map-2 expression and bromodeoxyuridine incorporation define molecularly distinct cell populations in the embryonic mouse forebrain" J Neuroscience, 14/11:6370-9383, 1994
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