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Accumulation of transcripts coding for prion protein in human astrocytes during infection with human immunodeficiency
W E Müller1, K Pfeifer, J Forrest
1Institut für Physiologische Chemie, Universität Mainz, Germany.
Abstract:
The abnormal isoforms of the normal cellular prion protein (PrP), also termed Scrapie-associated fibril protein, are assumed to be one causative factor of spongiform encephalopathies. The mRNA of PrP contains stem-loop structures which are very similar to the human immunodeficiency virus-1 (HIV-1) cis-acting sequence TAR within the LTR; both structures contain the pentanucleotide CUGGG in the loop, and the uridine- and adenine-bulge in the stem. In this study, using purified HIV-encoded trans-activator, Tat, and HIV-1 TAR-RNA or PrP-mRNA containing the stem-loop structure, we demonstrate by use of gel-retardation and filter binding assays that Tat binds to TAR- and PrP-RNA with the dissociation constants of 2.9 or 37.0 nM, respectively, at a molar ratio of 0.7 mol of Tat to 1 mol of RNA fragment. The Tat-RNA (TAR or PrP) complexes bind to protein(s) in the nuclear matrix, isolated from human astrocytes (glial fibrillary acidic protein positive brain cells). Infection of astrocytes with HIV-1 resulted in an increased level of PrP mRNA. The data presented led us to assume that certain sequences in the PrP mRNA might be targets for proteins acting in trans.
Insights
The human immunodeficiency virus-1 (HIV-1) trans-activator, Tat, binds to prion protein messenger RNA (PrP mRNA). This interaction may influence PrP mRNA levels in cells infected with HIV-1.
Area of Science:
- Molecular Biology
- Neuroscience
- Virology
Background:
- Abnormal prion protein (PrP) isoforms are implicated in spongiform encephalopathies.
- PrP mRNA shares structural similarities with the HIV-1 TAR RNA sequence.
Purpose of the Study:
- To investigate the interaction between HIV-1 Tat protein and PrP mRNA.
- To explore the functional consequences of this interaction in human astrocytes.
Main Methods:
- Gel-retardation and filter binding assays were used to assess Tat-RNA binding.
- Nuclear matrix proteins from human astrocytes were utilized.
- PrP mRNA levels were measured in HIV-1 infected astrocytes.
Main Results:
- HIV-1 Tat protein binds to both HIV-1 TAR RNA and PrP mRNA with distinct affinities.
- Tat-RNA complexes interact with proteins in the human astrocyte nuclear matrix.
- HIV-1 infection leads to elevated PrP mRNA levels in astrocytes.
Conclusions:
- PrP mRNA contains sequences that may be recognized by trans-acting proteins.
- The interaction between Tat and PrP mRNA could play a role in modulating PrP expression during HIV-1 infection.