LINCing the eukaryotic tree of life - towards a broad evolutionary comparison of nucleocytoplasmic bridging complexes

Abstract

The nuclear envelope is much more than a simple barrier between nucleoplasm and cytoplasm. Nuclear envelope bridging complexes are protein complexes spanning both the inner and outer nuclear envelope membranes, thus directly connecting the cytoplasm with the nucleoplasm. In metazoans, they are involved in connecting the cytoskeleton with the nucleoskeleton, and act as anchoring platforms at the nuclear envelope for the positioning and moving of both nuclei and chromosomes. Recently, nucleocytoplasmic bridging complexes have also been identified in more evolutionarily diverse organisms, including land plants. Here, I discuss similarities and differences among and between eukaryotic supergroups, specifically of the proteins forming the cytoplasmic surface of these complexes. I am proposing a structure and function for a hypothetical ancestral nucleocytoplasmic bridging complex in the last eukaryotic common ancestor, with the goal to stimulate research in more diverse emerging model organisms.

Keywords: Archeaplastida; Coiled-coil domain; Evolution; KASH protein; LINC complex; Opisthokonta; SUN protein.