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RNase H (fwd)

Brian Foley btf at t10.lanl.gov
Thu Apr 24 13:22:49 EST 1997


> >Is RNase H actually involved in the infection process or is
> >this another function of the multi-talented RT?  Can anyone
> >refer me to a good discussion of this topic??  Please respond
> >directly to me, as I am not a subscriber to HIV-biol (or virology).

A MedLine search at:
for "immunodeficiency virus RNAse"
results in over 200 articles matching.

Here is one:

Nucleic Acids Res 24 (9): 1719-1726 (1996) 

Relationship between plus strand DNA synthesis removal of
downstream segments of RNA by human immunodeficiency virus,
murine leukemia virus and avian myeloblastoma virus reverse

Fuentes GM, Fay PJ, Bambara RA

Department of Microbiology, University of Rochester,
School of Medicine and Dentistry, NY 14642,

During retroviral reverse transcription the genomic RNA is 
degraded by the RNase H activity of
reverse transcriptase (RT). Previous results suggest that 
after RNA-directed DNA synthesis,
fragments of RNA remain annealed to the newly synthesized 
DNA [DeStefano et al.(1991) J.
Biol.Chem. 266, 7423-7431]. These must be removed to allow 
synthesis of the second DNA strand.
We measured the ability of HIV-, AMV- and MuLV-RT to coordinate
DNA-dependent DNA
synthesis and removal of downstream segments of RNA. The 
substrates employed were DNA
templates having upstream DNA and downstream RNA primers. 
We found that none of the wild
type RTs elongated the upstream DNA without simultaneous 
degradation of the RNA. Consistent
with these results, HIV-, AMV- and MuLV-RT showed relatively 
higher affinity for RNA than for
DNA oligonucleotides bound to a DNA template. Differences 
were observed in the RNA
degradation and DNA extension patterns generated by the 
different RTs. AMV-RT degraded the
RNA to segments 11-12 nt long, and readily elongated 
the upstream DNA to the end of the
template. MuLV- and HIV-RT degraded the RNA primarily 
to segments 15-16 nt long. At low
concentrations of the latter two RTs, the DNA primer 
stalled when it encountered the 5'-end of the
RNA. In sufficient excess, all of the RTs elongated 
the upstream primer without stalling. Even
though we were unable to detect displacement of the 
downstream RNA by the wild type RTs,
MuLV- and HIV-RT lacking RNase H, were able to elongate 
the upstream DNA to the end of the
template without degradation of the RNA. This suggests 
that degradation of downstream pieces of
RNA is not absolutely required before synthesis of the 
plus strand DNA. The implications of these
findings for viral replication are discussed. 
|Brian T. Foley               btf at t10.lanl.gov                       |
|HIV Database                 (505) 665-1970                         |
|Los Alamos National Lab      http://hiv-web.lanl.gov/index.html     |
|Los Alamos, NM 87544  U.S.A. http://www.t10.lanl.gov/~btf/home.html |

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