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Characterization of the polymerase and RNase H activities of human foamy virus reverse transcriptase.

ABSTRACT: Foamy virus (FV) replication, while related to that of orthoretroviruses, differs at a number of steps. Several of these differences involve the reverse transcriptase (RT). There appear to be fewer RTs present in FV than in orthoretroviruses; we previously proposed that the polymerase of FV RT was more active than orthoretroviral RTs to compensate for the numerical difference. Here we present further characterization of the RT of FV. The polymerase activity of FV RT was greater than that of human immunodeficiency virus type 1 RT in a variety of assays. We also examined the RNase H activity of FV RT, and we propose that FV RT has a basic loop in the RNase H domain. Although the sequence of the basic loop of FV RT is different from the basic loop of either Moloney leukemia virus RNase H or Escherichia coli RNase H, the FV RT basic loop appears to have a similar function.

SUBMITTER: Boyer PL

PROVIDER: S-EPMC416499 | biostudies-literature | 2004 Jun

REPOSITORIES: biostudies-literature

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Characterization of the polymerase and RNase H activities of human foamy virus reverse transcriptase.

Boyer Paul L PL Stenbak Carolyn R CR Clark Patrick K PK Linial Maxine L ML Hughes Stephen H SH

Journal of virology 20040601 12

Foamy virus (FV) replication, while related to that of orthoretroviruses, differs at a number of steps. Several of these differences involve the reverse transcriptase (RT). There appear to be fewer RTs present in FV than in orthoretroviruses; we previously proposed that the polymerase of FV RT was more active than orthoretroviral RTs to compensate for the numerical difference. Here we present further characterization of the RT of FV. The polymerase activity of FV RT was greater than that of huma ...[more]

PMID: 15163704

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Project description:Reverse transcriptases (RTs) use their DNA polymerase and RNase H activities to catalyze the conversion of single-stranded RNA to double-stranded DNA (dsDNA), a crucial process for the replication of retroviruses. Foamy viruses (FVs) possess a unique RT, which is a fusion with the protease (PR) domain. The mechanism of substrate binding by this enzyme has been unknown. Here, we report a crystal structure of monomeric full-length marmoset FV (MFV) PR-RT in complex with an RNA/DNA hybrid substrate. We also describe a structure of MFV PR-RT with an RNase H deletion in complex with a dsDNA substrate in which the enzyme forms an asymmetric homodimer. Cryo-electron microscopy reconstruction of the full-length MFV PR-RT-dsDNA complex confirmed the dimeric architecture. These findings represent the first structural description of nucleic acid binding by a foamy viral RT and demonstrate its ability to change its oligomeric state depending on the type of bound nucleic acid. IMPORTANCE Reverse transcriptases (RTs) are intriguing enzymes converting single-stranded RNA to dsDNA. Their activity is essential for retroviruses, which are divided into two subfamilies differing significantly in their life cycles: Orthoretrovirinae and Spumaretrovirinae. The latter family is much more ancient and comprises five genera. A unique feature of foamy viral RTs is that they contain N-terminal protease (PR) domains, which are not present in orthoretroviral enzymes. So far, no structural information for full-length foamy viral PR-RT interacting with nucleic substrates has been reported. Here, we present crystal and cryo-electron microscopy structures of marmoset foamy virus (MFV) PR-RT. These structures revealed the mode of binding of RNA/DNA and dsDNA substrates. Moreover, unexpectedly, the structures and biochemical data showed that foamy viral PR-RT can adopt both a monomeric configuration, which is observed in our structures in the presence of an RNA/DNA hybrid, and an asymmetric dimer arrangement, which we observed in the presence of dsDNA.

Dataset Information

Characterization of the polymerase and RNase H activities of human foamy virus reverse transcriptase.

Publications

Characterization of the polymerase and RNase H activities of human foamy virus reverse transcriptase.

Similar Datasets

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