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Author Notes:

Correspondence: baek.kim@emory.edu

JAH and ST performed experiments.

GML, SR, DK and RFS contributed conceptually to the experimental design.

JAH, GML and BK wrote the manuscript.

FDG provided reagents.

All authors read and approved the final manuscript.

We would like to thank Waaqo Daddacha and Laura Nguyen for technical assistance with the HIV-1 RT-based dNTP assay.

We would also like to thank Michael Hirschman and Michele Daly for technical assistance.

The authors declare that they have no competing interests.


Research Funding:

This study was supported by NIH AI049781 (B.K.), GM104198 (B.K.), 5P30-AI-50409 Emory Centers for AIDS Research (CFAR), AI087390 (F. D-G), and the Department of Veterans Affairs.


  • Science & Technology
  • Life Sciences & Biomedicine
  • Virology
  • HIV-1
  • Monocytes-derived macrophages
  • Vpx
  • SAMHD1
  • dNTPs: virus-like particles
  • CD4(+) T-CELLS
  • VPX

dNTP pool modulation dynamics by SAMHD1 protein in monocyte-derived macrophages

Journal Title:



Volume 11


Type of Work:

Article | Final Publisher PDF


Background: SAMHD1 degrades deoxyribonucleotides (dNTPs), suppressing viral DNA synthesis in macrophages. Recently, viral protein X (Vpx) of HIV-2/SIVsm was shown to target SAMHD1 for proteosomal degradation and led to elevation of dNTP levels, which in turn accelerated proviral DNA synthesis of lentiviruses in macrophages. Results: We investigated both time-dependent and quantitative interplays between SAMHD1 level and dNTP concentrations during multiple exposures of Vpx in macrophages. The following were observed. First, SAMHD1 level was rapidly reduced by Vpx + VLP to undetectable levels by Western blot analysis. Recovery of SAMHD1 was very slow with less than 3% of the normal macrophage level detected at day 6 post Vpx treatment and only ~30% recovered at day 14. Second, dGTP, dCTP and dTTP levels peaked at day 1 post Vpx treatment, whereas dATP peaked at day 2. However, all dNTPs rapidly decreased starting at day 3, while SAMHD1 level was below the level of detection. Third, when Vpx pretreated macrophages were re-exposed to a second Vpx treatment at day 7, we observed dNTP elevation that had faster kinetics than the first Vpx + VLP treatment. Moreover, we performed a short kinetic analysis of the second Vpx treatment to find that dATP and dGTP levels peaked at 8 hours post secondary VLP treatment. dGTP peak was consistently higher than the primary, whereas peak dATP concentration was basically equivalent to the first Vpx + VLP treatment. Lastly, HIV-1 replication kinetics were faster in macrophages treated after the secondary Vpx treatments when compared to the initial single Vpx treatment. Conclusion: This study reveals that a very low level of SAMHD1 sufficiently modulates the normally low dNTP levels in macrophages and proposes potential diverse mechanisms of Vpx-mediated dNTP regulation in macrophages.

Copyright information:

© 2014 Hollenbaugh et al.; licensee BioMed Central Ltd.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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