System that controls cell division resembles a mosaic
Protein complex in cell nucleus developed from primal proteins
The protein complex that the cells of animals, plants, and fungi use to control cell division was created long ago from at least 40 different proteins. This could explain the overwhelming success of all cells with a cell nucleus, according to researchers at Utrecht University and the Hubrecht Institute. Their results were published in the scientific journal PNAS on 24 May.
“You might think that a fungus more closely resembles bacteria than it does us”, says Geert Kops, cell biologist at the Hubrecht Institute. “But that’s not the case. In contrast to the prokaryotic bacterial cells, the eukaryotic cells of fungi, plants, and animals all have a nucleus that stores the DNA.”
Although both types of cells can replicate their DNA and then divide it among two new daughter cells, the systems by which prokaryotes and eukaryotes distribute the DNA among the daughter cells are completely different. Eukaryotes use what is known as a ‘kinetochore’; a protein complex that might have been crucial in their success.
No intermediate form, and therefore indispensable
The kinetochore in every eukaryotic cell on Earth has a complex structure, while prokaryotic cells don’t have a kinetochore. In evolutionary theory, the absence of simple intermediate forms is an indication of the protein’s importance. Berend Snel, theoretical biologist at Utrecht University (UU): “That makes it even more relevant for us to find out how the protein complex developed. All of the kinetochores on Earth today should come from the same ancestor.”
Former PhD candidates Eelco Tromer (Hubrecht Institute) and Jolien van Hooff (UU) were able to unravel its lineage by combining an improved, more sensitive method for searching for comparable DNA sequences - and therefore relationships - with new insights into the composition of the protein complex.
Berend Snel: “We used 3D structures of the kinetochore’s sub-complexes that had been published by other scientists. By data mining through that information, we were able to determine how the system evolved. The protein complex appears to be a mosaic of at least 40 primordial proteins, which have been duplicated over and over again.”
Black hole of cell division
The publication provides insight into the development of life. Geert Kops, Hubrecht Institute: “An accurate, coordinated division is essential to a cell’s success. To me, the kinetochore is the black hole of eukaryotic cell division. We would very much like to know how the system developed, and how it functions in every organism on Earth. This work will contribute to that understanding.”
Mosaic origin of the eukaryotic kinetochore
Eelco Tromer*^, Jolien J.E. van Hooff*^, Geert J.P.L. Kops^ and Berend Snel*
PNAS, 24 May 2019
* Affiliated to Utrecht University
^ Affiliated to the Hubrecht Institute and Oncode Institute