Targeted recombination of exogenous DNA to its homologous chromosomal location is a potentially powerful tool for studying gene function, for creating animal models of disease, and for treating gene defects in humans. Unfortunately, targeted recombination in animal cells is masked by random integration into chromosomes, which occurs roughly 1000 times more frequently. As a consequence, gene-disruption and gene-replacement experiments of the sort that are commonplace in yeast are impractical in mammalian cells at present. For targeted approaches to contribute significantly to solving problems of gene function and disease, the proportion of targeted to random events must be increased. The objective of our proposed research is to understand the mechanisms of targeted and random recombination cells with a view toward increasing the ratio of targeted to random recombination events. We propose to develop a test system involving the APRT gene in its natural chromosomal context in CHO cells 1) to measure the relative proportions of targeted and random recombination into mammalian chromosomes and 2) to measure the relative frequencies of targeted integration and targeted gene conversions. Using this system, we will test two types of targeting substrates 1) to distinguish between break-repair models for targeted recombination in mammalian cells and 2) to determine which type of targeting substrate is more effective at promoting targeted recombination. In addition, we will test the effects of modifying the ends of targeting substrates in order to inhibit end-to-end ligation: 1) potentially increasing the fraction of substrates available for targeted recombination and 2) potentially decreasing their random integration into the chromosome. Finally, using a series of amplified mouse L cell lines, in which the ADA gene copy number ranges from 2 to 20,000 copies (all in the same chromosomal context), we will 1) measure the effect of target number on the frequency of targeted recombination and 2) screen for different efficiencies of targeted recombination at various sites within the amplified unit.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM038219-05
Application #
3294401
Study Section
Mammalian Genetics Study Section (MGN)
Project Start
1987-04-01
Project End
1992-03-31
Budget Start
1991-04-01
Budget End
1992-03-31
Support Year
5
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Baylor College of Medicine
Department
Type
Schools of Medicine
DUNS #
074615394
City
Houston
State
TX
Country
United States
Zip Code
77030
Chatterjee, Nimrat; Lin, Yunfu; Wilson, John H (2016) Mismatch repair enhances convergent transcription-induced cell death at trinucleotide repeats by activating ATR. DNA Repair (Amst) 42:26-32
Chatterjee, Nimrat; Lin, Yunfu; Yotnda, Patricia et al. (2016) Environmental Stress Induces Trinucleotide Repeat Mutagenesis in Human Cells by Alt-Nonhomologous End Joining Repair. J Mol Biol 428:2978-80
Chatterjee, Nimrat; Lin, Yunfu; Wilson, John H (2016) Fanconi anemia pathway regulates convergent transcription-induced cell death at trinucleotide repeats in human cells. Postdoc J 4:46-54
Lin, William Y; Wilson, John H; Lin, Yunfu (2013) Repair of chromosomal double-strand breaks by precise ligation in human cells. DNA Repair (Amst) 12:480-7
Mittelman, David; Wilson, John H (2013) The fractured genome of HeLa cells. Genome Biol 14:111
Lin, Yunfu; Leng, Mei; Wan, Ma et al. (2010) Convergent transcription through a long CAG tract destabilizes repeats and induces apoptosis. Mol Cell Biol 30:4435-51
Lin, Yunfu; Wilson, John H (2009) Diverse effects of individual mismatch repair components on transcription-induced CAG repeat instability in human cells. DNA Repair (Amst) 8:878-85
Dion, Vincent; Lin, Yunfu; Price, Brandee A et al. (2008) Genome-wide demethylation promotes triplet repeat instability independently of homologous recombination. DNA Repair (Amst) 7:313-20