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Interaction of the Ty3 reverse transcriptase thumb subdomain with template-primer.
Arkadiusz Bibillo1, Daniela Lener, Alok Tewari
1Reverse Transcriptase Biochemistry Section, Resistance Mechanisms Laboratory, HIV Drug Resistance Program, NCI, Frederick, National Institutes of Health, Frederick, Maryland 21702-1201, USA.
The Journal of Biological Chemistry
|June 10, 2005
Summary
Researchers identified key amino acid residues in the Ty3 retrotransposon reverse transcriptase (RT) thumb subdomain. These findings reveal specific interactions crucial for DNA polymerase and RNase H activities, offering insights into retroelement function.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Reverse transcriptase (RT) is essential for retrotransposon replication.
- The thumb subdomain of RT plays a critical role in nucleic acid binding and catalysis.
- Ty3 retrotransposon from Saccharomyces cerevisiae provides a model for studying RT structure-function relationships.
Purpose of the Study:
- To identify the thumb subdomain of Saccharomyces cerevisiae Ty3 reverse transcriptase (RT).
- To investigate the roles of specific amino acid residues within the Ty3 RT thumb subdomain in DNA polymerase and RNase H activities.
- To compare the functional and structural implications of the Ty3 RT thumb subdomain with that of human immunodeficiency virus type 1 (HIV-1) RT.
Main Methods:
- Amino acid sequence alignment to identify homologous regions between Ty3 RT and HIV-1 RT.
- Site-directed mutagenesis of specific Ty3 RT residues (Gln290, Phe292, Gly294, Asn297, Tyr298).
- Assays for DNA-dependent DNA synthesis using various substrates, including those with locked nucleic acid analogs and abasic lesions.
- Evaluation of RNase H activity.
Main Results:
- Identified amino acids 290-298 as the putative thumb subdomain of Ty3 RT, analogous to helix alphaH in HIV-1 RT.
- Mutations at Ty3 RT positions Tyr298, Gly294, and Asn297 suggest interactions with primer nucleotide -3, primer nucleotide -4, and template nucleotide -6, respectively.
- Substitution of Gln290 with Ala was tolerated, despite its high conservation.
- Mutations in the Ty3 RT thumb subdomain impacted both DNA polymerase and RNase H activities.
Conclusions:
- The Ty3 RT thumb subdomain residues Tyr298, Gly294, and Asn297 are involved in substrate binding during DNA synthesis.
- The Ty3 RT thumb subdomain plays a role in both DNA polymerase and RNase H functions.
- Ty3 RT may exhibit a closer spatial arrangement between its N- and C-terminal catalytic centers compared to HIV-1 RT.