Abstract

Eukaryotic cells organize some of its cellular components into membrane-less compartments through a process called liquid-to-liquid phase separation (LLPS). LLPS-driven compartments, also referred to as biomolecular condensates, emerge from transient interactions between intrinsically disordered proteins (IDPs) and other biomolecules, primarily RNA and DNA. Self-associating IDPs are key regulators of LLPS as they lack a 3-dimensional protein structure due to the abundance of charged, hydrophilic amino acids within its linear protein sequence. This compositional bias enables IDPs to maintain multiple weak interactions that result in selective localization of free-floating cytoplasmic molecules. Under preferable physical conditions, the localized molecules transition from dilute to molecule-rich phase forming a chemically unique gel-like condensate capable of performing biological functions.

Biomolecular condensates are prevalent inside the nucleus of eukaryotic cells and range in size from relatively large nucleoli to tiny nuclear speckles. The advances in recent research showed that phase separated states hold a central role in nucleus organization and functionalization; however, the intricacies of this topic are yet to be explored. In this literature review and the accompanying poster, three instances of biological phase transitions inside the nucleus, including heterochromatin gene regulation, transcriptional regulation by RNA polymerase II and ribosome assembly, will be discussed in detail. Specifically, we interpret the molecular mechanisms and biophysical aspects that form, segregate and localize LLPS condensates in the nuclear space to perform each of three nuclear functions. The purpose of this review is to summarize the existing information on the topic area and build a comprehensive understanding of the complex concept by presenting the information in a structured and coherent manner.

Department

Biological Sciences

Faculty Advisor

Don Nelson

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Phase Transitions in the Nucleus

Eukaryotic cells organize some of its cellular components into membrane-less compartments through a process called liquid-to-liquid phase separation (LLPS). LLPS-driven compartments, also referred to as biomolecular condensates, emerge from transient interactions between intrinsically disordered proteins (IDPs) and other biomolecules, primarily RNA and DNA. Self-associating IDPs are key regulators of LLPS as they lack a 3-dimensional protein structure due to the abundance of charged, hydrophilic amino acids within its linear protein sequence. This compositional bias enables IDPs to maintain multiple weak interactions that result in selective localization of free-floating cytoplasmic molecules. Under preferable physical conditions, the localized molecules transition from dilute to molecule-rich phase forming a chemically unique gel-like condensate capable of performing biological functions.

Biomolecular condensates are prevalent inside the nucleus of eukaryotic cells and range in size from relatively large nucleoli to tiny nuclear speckles. The advances in recent research showed that phase separated states hold a central role in nucleus organization and functionalization; however, the intricacies of this topic are yet to be explored. In this literature review and the accompanying poster, three instances of biological phase transitions inside the nucleus, including heterochromatin gene regulation, transcriptional regulation by RNA polymerase II and ribosome assembly, will be discussed in detail. Specifically, we interpret the molecular mechanisms and biophysical aspects that form, segregate and localize LLPS condensates in the nuclear space to perform each of three nuclear functions. The purpose of this review is to summarize the existing information on the topic area and build a comprehensive understanding of the complex concept by presenting the information in a structured and coherent manner.

 

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