Document Detail

The removal of RNA primers from DNA synthesized by the reverse transcriptase of the retrotransposon Tf1 is stimulated by Tf1 integrase.
MedLine Citation:
PMID:  22491446     Owner:  NLM     Status:  MEDLINE    
The Tf1 retrotransposon represents a group of long terminal repeat retroelements that use an RNA self-primer for initiating reverse transcription while synthesizing the minus-sense DNA strand. Tf1 reverse transcriptase (RT) was found earlier to generate the self-primer in vitro. Here, we show that this RT can remove from the synthesized cDNA the entire self-primer as well as the complete polypurine tract (PPT) sequence (serving as a second primer for cDNA synthesis). However, these primer removals, mediated by the RNase H activity of Tf1 RT, are quite inefficient. Interestingly, the integrase of Tf1 stimulated the specific Tf1 RT-directed cleavage of both the self-primer and PPT, although there was no general enhancement of the RT's RNase H activity (and the integrase by itself is devoid of any primer cleavage). The RTs of two prototype retroviruses, murine leukemia virus and human immunodeficiency virus, showed only a partial and nonspecific cleavage of both Tf1-associated primers with no stimulation by Tf1 integrase. Mutagenesis of Tf1 integrase revealed that the complete Tf1 integrase protein (excluding its chromodomain) is required for stimulating the Tf1 RT primer removal activity. Nonetheless, a double mutant integrase that has lost its integration functions can still stimulate the RT's activity, though heat-inactivated integrase cannot enhance primer removals. These findings suggest that the enzymatic activity of Tf1 integrase is not essential for stimulating the RT-mediated primer removal, while the proper folding of this protein is obligatory for this function. These results highlight possible new functions of Tf1 integrase in the retrotransposon's reverse transcription process.
Eytan Herzig; Nickolay Voronin; Amnon Hizi
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-04-04
Journal Detail:
Title:  Journal of virology     Volume:  86     ISSN:  1098-5514     ISO Abbreviation:  J. Virol.     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-05-09     Completed Date:  2012-07-09     Revised Date:  2013-06-26    
Medline Journal Info:
Nlm Unique ID:  0113724     Medline TA:  J Virol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  6222-30     Citation Subset:  IM    
Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
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MeSH Terms
DNA, Complementary / metabolism
HIV / enzymology
Integrases / genetics,  metabolism*
Leukemia Virus, Murine / enzymology
Mutant Proteins / genetics,  metabolism
Mutation, Missense
RNA / metabolism*
RNA-Directed DNA Polymerase / genetics,  metabolism*
Ribonuclease H / metabolism
Reg. No./Substance:
0/DNA, Complementary; 0/Mutant Proteins; 0/RNA primers; 0/Retroelements; 63231-63-0/RNA; EC 2.7.7.-/Integrases; EC DNA Polymerase; EC H

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