The GAR domain integrates functions that are necessary for the proper localization of fibrillarin (FBL) inside eukaryotic cells
Maria Y. Shubina,
Eugene A. Arifulin,
Dmitry V. Sorokin,
Mariya A. Sosina,
Maria A. Tikhomirova,
Marina V. Serebryakova,
Tatiana Smirnova,
Svyatoslav S. Sokolov,
Yana R. Musinova,
Eugene V. Sheval
Affiliations
Maria Y. Shubina
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
Eugene A. Arifulin
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
Dmitry V. Sorokin
Laboratory of Mathematical Methods of Image Processing, Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, Moscow, Russia
Mariya A. Sosina
Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
Maria A. Tikhomirova
Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
Marina V. Serebryakova
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
Tatiana Smirnova
Department of Cell Biology and Histology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
Svyatoslav S. Sokolov
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
Yana R. Musinova
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
Eugene V. Sheval
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
Fibrillarin (FBL) is an essential nucleolar protein that participates in pre-rRNA methylation and processing. The methyltransferase domain of FBL is an example of an extremely well-conserved protein domain in which the amino acid sequence was not substantially modified during the evolution from Archaea to Eukaryota. An additional N-terminal glycine–arginine-rich (GAR) domain is present in the FBL of eukaryotes. Here, we demonstrate that the GAR domain is involved in FBL functioning and integrates the functions of the nuclear localization signal and the nucleolar localization signal (NoLS). The methylation of the arginine residues in the GAR domain is necessary for nuclear import but decreases the efficiency of nucleolar retention via the NoLS. The presented data indicate that the GAR domain can be considered an evolutionary innovation that integrates several functional activities and thereby adapts FBL to the highly compartmentalized content of the eukaryotic cell.
