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Transcriptional regulation of human immunodeficiency virus type-1 in the central nervous system
thesis
posted on 2017-02-09, 05:30 authored by Cowley, Daniel JohnInfection with human immunodeficiency virus type-1 (HIV-1) is a significant
global health challenge. Since first identified as the aetiological agent of
acquired immunodeficiency syndrome (AIDS), approximately 60 million people
have been infected and 25 million people have died of HIV-related disease.
HIV-1 infection of the central nervous system (CNS) can lead to a number of
neurological complications, presenting clinically as a spectrum of disease from
asympotomatic neurological impairment to HIV-1 associated dementia (HAD).
Despite advances in antiretroviral therapies the neurological complications of
HIV-1 infection persist. Therefore, understanding the mechanisms of HIV-1
neuropathogenesis will help guide strategies designed to control HIV-1 within
the CNS.
HIV-1 transcription is regulated by the interaction of host and viral factors
with cis-acting sequences within the HIV-1 long terminal repeat (LTR). The
mechanisms regulating HIV-1 transcription in the CNS and their role in
neuropathogenesis remain unclear. In this study, the transcriptional regulatory
mechanisms in a panel of matched CNS- and lymphoid-tissue derived HIV-1
from subjects with HAD were examined. Compartmentalisation of HIV-1 LTR
sequences was identified between viruses derived from CNS and lymphoid
tissues. This compartmentalisation was associated with CNS specific sequence
variations in conserved transcription factor binding motifs and tissue specific
transcriptional activities, particularly in CNS derived astrocyte cells. By further
analysing the HIV-1 encoded transactivator (Tat), CNS specific Tat sequences
were identified in a subset of cohort subjects associated with heterogeneity in
Tat stimulated LTR transcriptional activity. Multiple amino acid changes with functional significance were observed in both CNS- and lymphoid-tissue derived
Tat. Notably, sequence changes were identified in Tat neurotoxic and
chemotactic domains that segregated CNS- and lymphoid-tissue derived Tat,
suggesting tissue specific differences in these properties.
Sequence differences that segregated matched CNS- and lymphoidtissue
derived LTR sequences were observed in the region spanning the three
Sp transcription factor-binding motifs of the basal/core promoter. This LTR
region has previously been reported to be essential for both basal and activated
transcription in lymphoid tissues. Electrophoretic mobility shift assays
performed using DNA probes with all three Sp sites in combination identified
differences between CNS and lymphoid-derived LTRs in overall Sp1 binding
affinity. When Sp sites were analysed in isolation the Sp1 binding activity of
CNS-derived promoter distal Sp sites (Sp-III) was markedly reduced when
compared to lymphoid-derived sites. Heterogeneity was observed in the Sp1
affinity of CNS and lymphoid-derived promoter medial (Sp-II) and promoter
proximal (Sp-I) Sp binding sites. Furthermore, sequence changes both within
and flanking the Sp sites were responsible for reduced Sp1 binding. Changes
at the promoter distal (Sp-III) site largely dictated overall LTR affinity. Reduced
Sp1 binding is predicted to influence LTR mediated transcriptional regulation.
Taken together, this study emphasises CNS specific HIV-1
transcriptional regulatory mechanisms with potential implications to
neuropathogenesis. The reduced Sp1 binding affinities and resulting decreased
transcriptional activity of CNS-derived LTRs indicate a reduced capacity to
initiate viral transcription and highlight mechanisms that control the
development of HIV-1 latency.
History
Principal supervisor
Steve WesselinghYear of Award
2011Department, School or Centre
Central Clinical SchoolAdditional Institution or Organisation
MedicineCampus location
AustraliaCourse
Doctor of PhilosophyDegree Type
DOCTORATEFaculty
Faculty of Medicine Nursing and Health SciencesUsage metrics
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