The conservation and diversity of the exons encoding the glycine and arginine rich domain of the fibrillarin gene in vertebrates, with special focus on reptiles and birds

• Published in: Gene Vol. 866; p. 147345
• Main Authors: Wang, Yi-Chun, Chang, Chien-Ping, Lai, Yu-Chuan, Chan, Chi-Ho, Ou, Shan-Chia, Wang, Sue-Hong, Li, Chuan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 25.05.2023
• Subjects: Animals; Arginine; Birds; chickens; domain; eukaryotic cells; Exon length; exons; Exons - genetics; Fibrillarin; Glycine; Glycine arginine rich (GAR) domain; Methyltransferases; phenylalanine; Reptiles; Reptiles - genetics; RNA; species; Vertebrates - genetics; Reptiles; Exon length; DFC; PBS; aa; SDMA; Glycine arginine rich (GAR) domain; rRNA; nt; myr; EST; MTase; ADMA; PRMT; snoRNA; FBL; RGG; SNP; RG; SMN; Fibrillarin; GAR; snoRNP
• ISSN: 0378-1119; 1879-0038; 1879-0038
• DOI: 10.1016/j.gene.2023.147345

•A nine-exon configuration of the fibrillarin gene is conserved in vertebrates.•Internal exons are of the same lengths except exon 2 and 3 encoding the GAR domain.•Reptiles have shorter exon 2 but longer exon 3 compared with other tetrapods.•Song birds have the shortest exon 2 and highly evolved exon 3. The nucleolar rRNA 2′-O-methyltransferase fibrillarin (FBL) contains a highly conserved methyltransferase domain at the C-terminus and a diverse glycine arginine-rich (GAR) domain at the N-terminus in eukaryotes. We found that a nine-exon configuration of fbl and exon 2–3 encoded GAR domain are conserved and specific in vertebrates. All internal exons except exon 2 and 3 are of the same lengths in different vertebrate lineages. The lengths of exon 2 and 3 vary in different vertebrate species but the ones with longer exon 2 usually have shorter exon 3 complementarily, limiting lengths of the GAR domain within a certain range. In tetrapods except for reptiles, exon 2 appears to be longer than exon 3. We specifically analyzed different lineages of reptiles for their GAR sequences and exon lengths. The lengths of exon 2 in reptiles are around 80–130-nt shorter and the lengths of exon 3 in reptiles are around 50–90 nt longer than those in other tetrapods, all in the GAR-coding regions. An FSPR sequence is present at the beginning of the GAR domain encoded by exon 2 in all vertebrates, and a specific FXSP/G element (X can be K, R, Q, N, and H) exist in the middle of GAR with phenylalanine as the 3rd exon 3-encoded amino acid residue starting from jawfish. Snakes, turtles, and songbirds contain shorter exon 2 compared with lizards, indicating continuous deletions in exon 2 and insertions/duplications in exon 3 in these lineages. Specifically, we confirmed the presence the fbl gene in chicken and validated the RNA expression. Our analyses of the GAR-encoding exons of fbl in vertebrates and reptiles should provide the basis for further evolutionary analyses of more GAR domain encoding proteins.