CBF-1 induces both establishment and maintenance of HIV latency via recruiting
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CBF-1 induces both establishment and maintenance of HIV latency via recruiting PcG corepressor complex at HIV LTR. Mudit Tyagi George Mason University, Manassas, Virginia, USA. Multiple mechanisms are involved in establishing HIV latency.

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Mudit Tyagi George Mason University, Manassas, Virginia, USA

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CBF-1 induces both establishment and maintenance of HIV latency via recruiting PcGcorepressor complex at HIV LTR

Mudit Tyagi

George Mason University,

Manassas, Virginia, USA


Multiple mechanisms are involved in establishing HIV latency

  • Quiescent T cells show an absence of transcription factors such as NF-kB and NF-AT restricting initiation (Nabel, Kinoshita)

  • Quiescent T cells show reduced levels of P-TEFb, limiting transcription elongation and Tat activity (Rice, Karn)


Are there specific repressors of HIV LTR promoter, which are higher in resting T cells than their active counterparts.


CBF-1 Levels Rapidly Fall after T-cell Activation

B. HIV (mRNA)

A. CBF-1 (mRNA)


CBF-1 facilitates HIV latency in both transformed and primary CD4+ T cells

CBF-1 plays important role in HIV latency, as its knockdown in latently infected T cells reactivates latent HIV proviruses

CBF-1 inhibits HIV transcription by recruiting histonedeacetylases (HDAC) containing corepressorcomplexes


CBF-1 recruited PcG corepressor complex

facilitate HIV latency establishment

Nucleosome-1 (+30 to +134)

Scrambled shRNA

CBF-1 shRNA

Input DNA %


Polycomb Group corepressor complex

  • PcG complex carry variety of enzymes known to induce different repressive epigenetic modifications. Thus, PcG complex induce several layers of repressive epigenetic modifications involving both histones and DNA.

    PcG complex is known to play important role in both inducingand maintaining the silencing of several cellular genes,including transcriptional repression of the endogenous retroviruses and maintaining the long-term silencing of X chromosome.


CBF-1 recruited PcG corepressor complex

facilitate HIV latency maintenance too

Nucleosome-1 (+30 to +134)

Scrambled shRNA

CBF-1 shRNA

Input DNA %


PcG corepressor complex knockdown results in the reactivation of latent HIV proviruses

Aza-dC (5 uM)

-

+

+

+

+

+

+

+

Luciferase counts


Conclusions

CBF-1 is a potent and specific inhibitor of HIV transcription

CBF-1 performs its function by recruiting PcG corepressor complex at HIV LTR

Like an ideal repressors CBF-1 levels goes down following T cell activation.

Multiple chromatin modifying mechanisms are involved

in regulating gene expression from latent HIV proviruses

Inhibitors of PcG corepressor complex may play useful role for the induction strategies designed to eradicate latent viral pools in HIV patients.


Acknowledgements

Prof. Jonathan Karn


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