Biological complexity: nucleolus 'glue' (Introduction)

by David Turell , Monday, February 26, 2018, 20:22 (2462 days ago) @ David Turell

The nucleolus is a membraneless blob in the nucleus and is held together by a protein within it:

https://phys.org/news/2018-02-reveals-key-mechanism-cell-smart.html

"The protein, nucleophosmin, is a kind of "smart glue" in a structure called the nucleolus inside the cell's nucleus. In the nucleolus, nucleophosmin helps organize and regulate the construction of ribosomes—the biological machines that assemble proteins using their RNA genetic code as a guide.

"Nucleophosmin is critical to the liquid-like structure of the nucleolus called a membrane-less organelle. That is because unlike cell structures like the nucleus, the nucleolus is not enclosed in membranes. Instead, the nucleolus and other such organelles are something like the colorful undulating blobs in lava lamps—dynamically forming, shifting and fusing.

***

"In earlier studies, Kriwacki and colleagues had discovered how nucleophosmin binds to proteins and RNA to foster phase separation, as well as ribosomes' assembly. However, their studies of nucleophosmin were yielding results hinting that its "heterotypic" reactions—those with proteins other than itself and RNA—did not fully explain how part of the molecule called the intrinsically disordered region functioned.

***

"The experiments point to how the intrinsically disordered region undergoes changes as ribosomes are assembled and the makeup of the nucleolus changes. The changes were to increase homotypic interactions, or within the nucleophosmin molecule itself. The research also revealed how nucleophosmin interacts with another protein called SURF6. Scientists discovered SURF6 acts as a partner to nucleophosmin in creating and maintaining the loose scaffolding that holds the fluid nucleolus together.

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"The experiments revealed important new details of the mechanism by which the smart glue nucleophosmin changes its internal conformation as the liquid-like nucleolus facilitates ribosome assembly. At an early stage of the process, its primary job is to shepherd RNA and proteins to assemble ribosomes. But as the glue molecule hands off its cargo as ribosomes form, the glue molecule adjusts itself homotypically to interact with other glue molecules.
This cross-linking of nucleophosmin proteins constitutes a kind of buffering, in which nucleophosmin helps maintain the liquid consistency of the nucleolus. In this buffering, the homotypic mechanism competes with nucleophosmin's heterotypic mechanisms by which it attaches to RNA and proteins in helping assemble ribosomes."

Comment: Just more evidence of the complexity of cell function. Requires design, not chance. Ribosomes are an integral part of the RNA messenger system, vital to life's functions and continual existence.