# Assembly, maturation, and structures of HIV Gag, Gag-Pol and Pol, and PFV polyproteins

> **NIH NIH U54** · SEATTLE CHILDREN'S HOSPITAL · 2021 · $569,587

## Abstract

ABSTRACT
Gag is capable of self-assembly in vitro, although it is generally accepted that host factors play a decisive role
for immature Gag trafficking. Although many of the cellular proteins and mechanisms co-opted for viral budding
and release are well understood, the full identity and the role of cellular proteins participating in immature Gag
assembly remains incomplete. This Project focuses on identifying the composition of cellular factors
interacting with Gag/Gag-Pol throughout the Gag assembly pathway contributing to both the dynamic
assembly and cellular trafficking of Gag. To provide fundamental information on Gag assembly, early steps will
be interrogated in vitro at the single molecule level and later in cells. Computational methodologies will also
integrate the structural and biophysical findings into coherent structural models of higher-order assemblies.
Importantly, the structure of the first retroviral polyprotein, the protease-reverse transcriptase fusion protein
of prototype foamy virus has been solved. This sets the stage for additional and important structural
characterization of more complex retroviral polyproteins, which is required for understanding how cellular host
factor interactions contribute to Gag and Gag-Pol assembly.
The proposed investigations will strongly leverage the complementary scientific expertise within and
collaborative nature of the HIVE Center and take advantage of cutting-edge technologies available to address
the following Specific Aims: Aim 1. Pulse-labeling and quantitative mass spectrometry to characterize Gag
and Gag-Pol, assembly intermediates including associated proteins, and RNA, with subsequent functional
analysis (collaborators are: Williamson, Lyumkis, Marcotrigiano, Arnold, Griffin, Torbett); Aim 2. Single-
molecule analysis of Gag assembly in vitro and in vivo to gain insight into specific RNA contributions and Gag
oligomerization required for Gag assembly (collaborators are: Millar, Musier-Forsyth, Torbett, Williamson); Aim
3. Structural studies of Gag, Gag-Pol and Pol of HIV-1 and PFV (collaborators are: Arnold, Marcotrigiano,
Lyumkis, Griffin, Torbett, Williamson); and Aim 4. Mesoscale modeling of Gag during assembly (collaborators
are: Olson, Levy, Goodsell).
Understanding the temporal interplay of cellular factors contributing to immature Gag assembly and
progression, as well as the strategic role of Gag-Pol, and elucidating the structural basis for these interactions
will provide a more comprehensive understanding of an area in retroviral biology that is currently not well
understood. Elucidating the structural basis of identified cellular factors that interact with immature Gag and
Gag-Pol will allow development of novel small chemical probes for further interrogation of these interactions.

## Key facts

- **NIH application ID:** 10242906
- **Project number:** 5U54AI150472-11
- **Recipient organization:** SEATTLE CHILDREN'S HOSPITAL
- **Principal Investigator:** Bruce Edward Torbett
- **Activity code:** U54 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $569,587
- **Award type:** 5
- **Project period:** 2012-09-01 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10242906

## Citation

> US National Institutes of Health, RePORTER application 10242906, Assembly, maturation, and structures of HIV Gag, Gag-Pol and Pol, and PFV polyproteins (5U54AI150472-11). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10242906. Licensed CC0.

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