Abstract
The mechanistic evolutionary origin of the eukaryotic cell nucleus remains unknown. Among several plausible hypotheses, the most controversial is that large DNA viruses, such as poxviruses, led to the emergence of the eukaryotic cell nucleus. Several recent findings, including the discovery of a nucleus-like structure in prokaryotic viruses and prokaryotes possessing nucleus-like inner membranes, suggest genomic DNA compartmentalization not only in eukaryotes but also in prokaryotes. The sophisticated viral machinery of mimiviruses is thought to resemble the eukaryotic nucleus: DNA replicates both inside the viral factory and nucleus, which is at least partially surrounded by membranes and is devoid of ribosomes. Furthermore, several features of the recently identified Acanthamoeba castellanii medusavirus suggest that the evolutionary relationship between ancestral viral factory and eukaryotic nucleus. Notably, Ran, DNA polymerase, and histones show molecular fossils of lateral transfer of nuclear genes between the virus and host. These results suggest viral innovation in the emergence of the eukaryotic nucleus. According to these results, a new scenario explaining the origin of the eukaryotic nucleus from the perspective of viral participation is proposed. This new scenario could substantially impact the study of eukaryogenesis and stimulate further discussion about viral contributions to the evolution of the eukaryotic nucleus.
Highlights
The eukaryotic cell nucleus is a double-membrane-enclosed organelle that contains genetic material and functions as a gene expression platform
Medusavirus and the Origin of the Nucleus. These hypotheses account for and explain the driving force and evolutionary pressures, they fail to portray the precise process underlying eukaryotic nucleus evolution. This process, which occurred in the period between the first eukaryotic common ancestor (FECA) and the last eukaryotic common ancestor (LECA), results in genomic DNA being surrounded by lipid bilayers; compartmentalizing genomic DNA
This review provides an update on the theory of the viral origin of the eukaryotic nucleus and discusses future research directions
Summary
The eukaryotic cell nucleus is a double-membrane-enclosed organelle that contains genetic material and functions as a gene expression platform. Several studies, including the synthesis of nucleus-like structures in bacterial cells by a virus, and re-construction of inner membranes of host cells by some DNA and RNA viruses, strongly supported the putative viral commitment to eukaryogenesis (Miller and Krijnse-Locker, 2008; Chaikeeratisak et al, 2017).
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