posted on 2020-12-08, 12:46authored byRahul Sureka, Rakesh Mishra
Compared
to prokaryotic
cells, a typical
eukaryotic cell is much more complex along with its endomembrane system
and membrane-bound organelles. Although the endosymbiosis theories
convincingly explain the evolution of membrane-bound organelles such
as mitochondria and chloroplasts, very little is understood about
the evolutionary origins of the nucleus, the defining feature of eukaryotes.
Most studies on nuclear evolution have not been able to take into
consideration the underlying structural framework of the nucleus,
attributed to the nuclear matrix (NuMat), a ribonucleoproteinaceous
structure. This can largely be attributed to the lack of annotation
of its core components. Since NuMat has been shown to provide a structural
platform for facilitating a variety of nuclear functions such as replication,
transcription, and splicing, it is important to identify its protein
components to better understand these processes. In this study, we
address this issue using the developing embryos of Drosophila melanogaster and Danio
rerio and identify 362 core NuMat proteins that are
conserved between the two organisms. We further compare our results
with publicly available Mus musculus NuMat dataset and Homo sapiens cellular
localization dataset to define the core homologous NuMat proteins
consisting of 252 proteins. We find that of them, 86 protein groups
have originated from pre-existing proteins in prokaryotes. While 36
were conserved across all eukaryotic supergroups, 14 new proteins
evolved before the evolution of the last eukaryotic common ancestor
and together, these 50 proteins out of the 252 core conserved NuMat
proteins are conserved across all eukaryotes, indicating their indispensable
nature for nuclear function for over 1.5 billion years of eukaryotic
history. Our analysis paves the way to understand the evolution of
the complex internal nuclear architecture and its functions.