ИСТИНА

Cajal bodies (CBs), subnuclear compartments physically and functionally associated with nucleoli, participates in the maturation of splicing small nuclear ribonucleoproteins (snRNPs) and facilitates their modification and assembly via small CB specific RNAs (scaRNAs). Coilin, a major structural scaffolding protein necessary for CB formation, composition and activity, is predominantly found in CBs, but is also distributed throughout the nucleoplasm. The predictions made by the web-services FoldIndex and Disopred and analysis of the physical properties of deletion mutants demonstrate that Atcoilin contains extensive disordered regions and consists of three main domains: a N-terminal globular domain (NOD), an internal completely disordered domain (IDD) and a C-terminal region containing a presumable Tudor-like domain adjacent to a disordered C-terminus (CTD). Despite the low homology in amino acid sequences, human, animal coilins and coilin-like proteins of various plant species have a high level of structural and organizational similarity. Atcoilin binds RNA effectively, non-specifically and has three RNA-binding sites: two sets of basic amino acids in the NOD and one set in the IDD. The Atcoilin NOD being rather conserved across species has a globular structure that might be described as an ubiquitin-like fold in accordance to predictions made by bioinformatic web-services QUARK and LOMETS. Atomic force microscopy and Dinamic light scattering methods demonstrate that the interaction with RNA induces the multimerization of the Atcoilin molecules, with a consequence of the structural alterations in the NOD but not in the IDD or the CTD. It is known that proper formation of functional CBs depends on multiple factors. The Atcoilin-RNA interaction might be an additional key factor, which facilitates proper assembly of a scaffold required for correct CB formation