Temperature-induced DNA density transition in phage λ capsid revealed with contrast-matching SANS

Published

October 30, 2023

Author(s)

Jose Villanueva Valencia, Efthymios Tsimtsirakis, Susan N. Krueger, Alex Evilevitch

Abstract

Structural details of a genome packaged in a viral capsid are essential for understanding how the structural arrangement of a viral genome in a capsid controls its release dynamics during infection, which critically affects viral replication. We previously found a temperature-induced, solid-like to fluid-like mechanical transition of packaged λ-genome that leads to rapid DNA ejection. However, an understanding of the structural origin of this transition was lacking. Here, we use small-angle neutron scattering (SANS) to reveal the scattering form factor of dsDNA packaged in phage λ capsid by contrast matching the scattering signal from the viral capsid with deuterated buffer. We used small-angle X-ray scattering and cryoelectron microscopy reconstructions to determine the initial structural input parameters for intracapsid DNA, which allows accurate modeling of our SANS data. As result, we show a temperature-dependent density transition of intracapsid DNA occurring between two coexisting phases—a hexagonally ordered high-density DNA phase in the capsid periphery and a low-density, less-ordered DNA phase in the core. As the temperature is increased from 20 °C to 40 °C, we found that the core-DN phase undergoes a density and volume transition close to the physiological temperature of infection (37 °C). The transition yields a lower energy state of DNA in the capsid core due to lower density and reduced packing defects. This increases DNA mobility, which is required to initiate rapid genome ejection from the virus capsid into a host cell, causing infection. These data reconcile our earlier findings of mechanical DNA transition in phage.

Citation

Proceedings of the National Academy of Sciences

Volume

120

Issue

45

Pub Type

Journals

Download Paper

https://doi.org/10.1073/pnas.2220518120

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Keywords

phage lambda, small angle scattering, contrast matching, DNA packaging, viral replication

Citation

Villanueva Valencia, J. , Tsimtsirakis, E. , Krueger, S. and Evilevitch, A. (2023), Temperature-induced DNA density transition in phage λ capsid revealed with contrast-matching SANS, Proceedings of the National Academy of Sciences, [online], https://doi.org/10.1073/pnas.2220518120, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935945 (Accessed December 26, 2024)