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J Virol, August 1998, p. 6805-6812, Vol. 72, No. 8
Department of Biochemistry, University of
Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical
School, Piscataway, New Jersey 08854,1 and
Universidad Austral de Chile, Valdivia, Chile2
Received 21 January 1998/Accepted 15 May 1998
Retroviral reverse transcriptase-associated RNase H enzymes are
responsible for degradation of viral RNA, including removal of the tRNA
primer after plus-strand strong-stop synthesis and cleavage of the
polypurine tract primer. These activities are required for the complex
viral replication and result in generation of the long terminal
repeats. The human immunodeficiency virus type 1 (HIV-1) RNase H domain
has been expressed independently of the polymerase domain and possesses
Mn2+-dependent activity with a hexahistidine tag. The
isolated domain maintains the ability to specifically remove a tRNA
primer mimic. In this study, the substrate determinants for recognition
of the cognate tRNA3Lys are defined. Model substrates
were constructed which mimic the RNA-DNA hybrid obtained from
plus-strand strong-stop synthesis. Deletion substrates containing only
12, 9, or 6 positions of the tRNA primer were capable of being cleaved
by the isolated RNase H domain. Mismatch and bromodeoxyuridine
mutagenesis analysis indicated that positions 2, 3, 4, and 6, when
mutated, affected the specificity of RNase H activity. Substitution
substrates indicated that positions 4 and 6 within the RNA primer were
important for recognition and cleavage by the HIV-1 isolated RNase H
domain. Moloney murine leukemia virus-HIV-1 hybrid substrates were
constructed which demonstrated that changes to HIV-1 sequences at
positions 4 and 6 were sufficient but not optimal for regaining
cleavage by the isolated HIV-1 RNase H domain. Optimal site-specific
cleavage between the terminal ribonucleotide A and ribonucleotide C
requires additional sequences beyond the first six positions but less
than nine.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Sequence Requirements for Removal of tRNA by an
Isolated Human Immunodeficiency Virus Type 1 RNase H Domain
and
*
Corresponding author. Mailing address: Department of
Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854. Phone: (732) 235-5048. Fax: (732) 235-4783. E-mail:
Roth{at}waksman.rutgers.edu.
Present address: Department of Molecular Biology and Genetics,
Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185.
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