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Molecular and Cellular Biology, November 2005, p. 9209-9220, Vol. 25, No. 21
0270-7306/05/$08.00+0     doi:10.1128/MCB.25.21.9209-9220.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

The L1Tc C-Terminal Domain from Trypanosoma cruzi Non-Long Terminal Repeat Retrotransposon Codes for a Protein That Bears Two C₂H₂ Zinc Finger Motifs and Is Endowed with Nucleic Acid Chaperone Activity

Sara R. Heras,¹ Manuel C. López,¹ José Luis García-Pérez,^1, Sandra L. Martin,² and M. Carmen Thomas^1*

Departamento de Biología Molecular, Instituto de Parasitología y Biomedicina "López Neyra," CSIC, 18100 Granada, Spain,¹ Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado 80045²

Received 11 January 2005/ Returned for modification 4 April 2005/ Accepted 5 August 2005

L1Tc, a non-long terminal repeat retrotransposon from Trypanosoma cruzi, is a 4.9-kb actively transcribed element which contains a single open reading frame coding for the machinery necessary for its autonomous retrotransposition. In this paper, we analyze the protein encoded by the L1Tc 3' region, termed C2-L1Tc, which contains two zinc finger motifs similar to those present in the TFIIIA transcription factor family. C2-L1Tc binds nucleic acids with different affinities, such that RNA > tRNA > single-stranded DNA > double-stranded DNA, without any evidence for sequence specificity. C2-L1Tc also exhibits nucleic acid chaperone activity on different DNA templates that may participate in the mechanism of retrotransposition of the element. C2-L1Tc promotes annealing of complementary oligonucleotides, prevents melting of perfect DNA duplexes, and facilitates the strand exchange between DNAs to form the most stable duplex DNA in competitive displacement assays. Mapping of regions of C2-L1Tc using specific peptides showed that nucleic acid chaperone activity required a short basic sequence accompanied by a zinc finger motif or by another basic region such as RRR. Thus, a short basic polypeptide containing the two C₂H₂ motifs promotes formation of the most stable duplex DNA at a concentration only three times higher than that required for C2-L1Tc.

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* Corresponding author. Mailing address: Departamento de Biología Molecular, Instituto de Parasitología y Biomedicina "López Neyra," CSIC, Avda del Conocimiento s/n, 18100 Granada, Spain. Phone: 34 958 181662. Fax: 34 958 181632. E-mail: mcthomas{at}ipb.csic.es.

Present address: Departments of Human Genetics and Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109-0618.

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Molecular and Cellular Biology, November 2005, p. 9209-9220, Vol. 25, No. 21
0022-538X/05/$08.00+0     doi:10.1128/MCB.25.21.9209-9220.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Heras, S. R., Lopez, M. C., Olivares, M., Thomas, M. C. (2007). The L1Tc non-LTR retrotransposon of Trypanosoma cruzi contains an internal RNA-pol II-dependent promoter that strongly activates gene transcription and generates unspliced transcripts. Nucleic Acids Res 35: 2199-2214 [Abstract] [Full Text]