LTR-containing retrotransposons and retroviruses represent two related branches on the phylogenetic tree of reverse transcriptase (RT)-containing mobile genetic elements. Both types of elements use the RNA-dependent DNA polymerase, RT, to replicate their RNA genomes into double strand DNA which is then inserted into a host genome. The movement of retrotransposons within a genome can be harmful, resulting in genomic instability, cancer, sterility and mutations. On the other hand retrotransposons actively contribute to the evolution of their hosts' genomes. We have a long term interest in the replication mechanisms utilized by retrotransposon Tyl to maintain itself as an endogenous family of mobile elements in its host organism Saccharomyces cerevisiae. Tyl is a particularly useful experimental system to study transposition because it is so easily manipulated, because its natural host is such a genetically tractable organism, and because the steps in its replication are so closely related to the steps involved in retroviral replication. Since DNA polymerases replicate and transmit vital genetic information, the fidelity of their synthesis is a crucial biochemical determinant of their functional capacity. We have found that Tyl RT is an error prone polymerase, that generates errors at specific sites by a novel mechanism. We propose (Aim 1) to explore this new mutagenic mechanism genetically and biochemically, and determine the consequences of this process to Tyl replication fitness. Further, we will identify and characterize additional mutagenic mechanisms employed by Tyl RT during replication. We have created and are characterizing a novel mutation in the active site of Tyl RT which can still synthesize DNA but is blocked for transposition. This defect is suppressible by mutations in both the RNase H and polymerase domains of RT. We plan (Aim 2) to use this novel mutant to examine the distinctions between polymerization and replication, and more broadly, to understand the interactions between protein domains during Tyl replication. Further we will determine whether the properties of this novel mutant are generalizable to the ubiquitous family of retrotransposons whose RTs have not previously been studied.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM060534-01A2
Application #
6331442
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Program Officer
Wolfe, Paul B
Project Start
2001-05-01
Project End
2005-04-30
Budget Start
2001-05-01
Budget End
2002-04-30
Support Year
1
Fiscal Year
2001
Total Cost
$225,113
Indirect Cost
Name
Rutgers University
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
038633251
City
New Brunswick
State
NJ
Country
United States
Zip Code
08901
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Kim, Dennis D Y; Kim, Thomas T Y; Walsh, Thomas et al. (2004) Widespread RNA editing of embedded alu elements in the human transcriptome. Genome Res 14:1719-25
Pandey, Manjula; Patel, Smita; Gabriel, Abram (2004) Insights into the role of an active site aspartate in Ty1 reverse transcriptase polymerization. J Biol Chem 279:47840-8
Wilhelm, Francois-Xavier; Wilhelm, Marcelle; Gabriel, Abram (2003) Extension and cleavage of the polypurine tract plus-strand primer by Ty1 reverse transcriptase. J Biol Chem 278:47678-84
Wilhelm, M; Uzun, O; Mules, E H et al. (2001) Polypurine tract formation by Ty1 RNase H. J Biol Chem 276:47695-701