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Embryonic stem cells use ZFP809 to silence retroviral DNAs


Embryonic stem cells (ESCs) and other primitive stem cells of mice have been known for more than 30 years to potently block retrovirus replication1. Infection of ESCs by the murine leukaemia viruses (MLVs) results in the normal establishment of integrated proviral DNA, but this DNA is then transcriptionally silenced, preventing further viral spread. The repression is largely mediated by trans-acting factors that recognize a conserved sequence element termed the primer binding site, an 18-base pair sequence complementary to the 3′ end of a cellular transfer RNA2,3,4,5,6. A specific tRNA is annealed to the primer binding site sequence of the viral genomic RNA, and is used to prime DNA synthesis7. This same sequence in the context of the integrated proviral DNA is targeted for silencing in ESCs. We have recently shown that a large protein complex binding to the primer binding site in ESCs contains TRIM28 (refs 8, 9), a well-characterized transcriptional co-repressor10,11,12. An important question remains as to the identity of the factor that directly recognizes integrated retroviral DNAs and recruits TRIM28 to mediate their specific silencing. Here we identify the zinc finger protein ZFP809 as the recognition molecule that bridges the integrated proviral DNA and TRIM28. We show that expression of ZFP809 is sufficient to render even differentiated cells highly resistant to MLV infection. Furthermore, we demonstrate that ZFP809 is able to potently block transcription from DNA constructs of human T-cell lymphotropic virus-1 (HTLV-1), which use the same primer tRNA. These results identify ZFP809 as a DNA-binding factor that specifically recognizes a large subset of mammalian retroviruses and retroelements, targeting them for transcriptional silencing. We propose that ZFP809 evolved as a stem-cell-specific retroviral restriction factor, and therefore constitutes a new component of the intrinsic immune system of stem cells.

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Figure 1: Identification of candidate PBS Pro DNA-binding factors.
Figure 2: Reconstitution of the PBS Pro binding complex with recombinant proteins.
Figure 3: Stable expression of ZFP809 in 293A cells leads to reconstitution of the PBS silencing complex in vivo.
Figure 4: Expression of ZFP809 in a differentiated cell line causes a potent block to the replication of PBS Pro -using retroviruses.


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This work was supported by Public Health Service grant R37 CA 30488 from the National Cancer Institute. We thank D. Derse, F. Bouamr and E. Barklis for their generosity with reagents. We are grateful to M. de los Santos, H. Nickerson and M. A. Gawinowicz (Protein Core Facility Columbia University) for technical assistance. We would also like to thank P. Adusumilli, M. Banes, M. Bilsky, J. Yamada and co-workers, without whose help this paper would never have been written. D.W. is an Associate, and S.P.G. is an Investigator of the Howard Hughes Medical Institute.

Author Contributions D.W. performed the experiments and analysed the data. D.W. and S.P.G. designed the study and wrote the manuscript.

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Correspondence to Stephen P. Goff.

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Wolf, D., Goff, S. Embryonic stem cells use ZFP809 to silence retroviral DNAs. Nature 458, 1201–1204 (2009).

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