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Newly discovered Medusavirus give new insights on how organisms and viruses co-evolved

Date:
March 25, 2019
Source:
Kyoto University
Summary:
Researchers find a new giant virus in the hot springs of northern Japan. It's unique genetic makeup of histones and capsid proteins brings new insight into virus evolution.
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Scientists are constantly discovering new species.

A research team consisting of scientists from Kyoto University, Tokyo University of Science, National Institute for Physiological Sciences, and Tokyo Institute of Technology, report in the Journal of Virology the Medusavirus, a unique giant virus that gives pause to current theory on viral evolution.

The name Medusavirus was given for the effect this virus has on its host, Acanthamoeba castellanii. Once infected, the amoeba forms cysts, a phenomenon called encystment. This is a typical response to environments hostile to survival, and leaves the amoeba with a hard, protective covering. Perhaps it was not a coincidence then that Medusavirus was found in the hot springs in northern Japan, the first giant virus to have been isolated from a heated environment.

Along with the location of its discovery, Medusavirus holds a number of distinguishing features compared with other giant viruses. Its DNA codes for all five types of histones, the key proteins that help compact DNA within the nucleus. In fact, no other known virus has all five types. Further, Medusavirus encoded neither RNA polymerase nor DNA topoimerase II, whereas all other giant viruses encode at least one.

These features could explain why the replication of Medusavirus DNA begins and completes in the host nucleus to eventually fill the amoeba nucleus with viral DNA, which again is unlike other giant viruses.

Moreover, the morphology of the capsid surface was unique, in that it was covered with an extraordinary number of spherical-headed spikes. In addition, the amoeba genome encoded several capsid surface proteins.

The existence of histone genes in Medusavirus and capsid protein genes in amoeba suggest lateral gene transfer going both directions -- host-to-virus and virus-to-host.

Overall, the findings suggest that Medusavirus offers a new model for host-virus co-evolution and that the Medusavirus is a new family of large DNA viruses.


Story Source:

Materials provided by Kyoto University. Note: Content may be edited for style and length.


Journal Reference:

  1. Genki Yoshikawa, Romain Blanc-Mathieu, Chihong Song, Yoko Kayama, Tomohiro Mochizuki, Kazuyoshi Murata, Hiroyuki Ogata, Masaharu Takemura. Medusavirus, a novel large DNA virus discovered from hot spring water. Journal of Virology, 2019; DOI: 10.1128/JVI.02130-18

Cite This Page:

Kyoto University. "Newly discovered Medusavirus give new insights on how organisms and viruses co-evolved." ScienceDaily. ScienceDaily, 25 March 2019. <www.sciencedaily.com/releases/2019/03/190325110300.htm>.
Kyoto University. (2019, March 25). Newly discovered Medusavirus give new insights on how organisms and viruses co-evolved. ScienceDaily. Retrieved March 28, 2024 from www.sciencedaily.com/releases/2019/03/190325110300.htm
Kyoto University. "Newly discovered Medusavirus give new insights on how organisms and viruses co-evolved." ScienceDaily. www.sciencedaily.com/releases/2019/03/190325110300.htm (accessed March 28, 2024).

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