Investigations on Cellular Localization of Coiled-Coil Domain-Containing Protein 43 (CCDC43) Under Stress Conditions

Coiled-coil domain containing (CCDC) family proteins regulate multiple biological functions in the cell. These domain structures have physical properties favorable for liquid-liquid phase separation (LLPS) phenomena, which play important roles in cell biology dynamics. LLPS is a fundamental mechanism in forming membrane-less organelles, including stress granules (SG) and P-body, nucleolus, PML nuclear body, Cajal bodies, nuclear speckles, and centrosomes. One of the new members of the CCDC protein family is CCDC43. In this study, sequence-based analyses of CCDC43, performed as a first step to understanding the role of CCDC43 in the cellular network, revealed the LLPS potential of the protein. We report that CCDC43, which has an evolutionarily conserved protein sequence, structurally possesses RNA-binding sites and its amino acid composition analysis may show an aggregation propensity and LLPS behavior under cellular conditions. CCDC43 is known to show a diffuse localization in the cytoplasm. We investigated whether this cellular localization is present in SGs whose formation is based on LLPS. We found that CCDC43 does not aggregate at SGs under given stress conditions. These data provide the first insights into the intracellular behavior and roles of CCDC43 in a disease-independent manner.