Characterization of AtNUC-L1 reveals a central role of nucleolin in nucleolus organization and silencing of AtNUC-L2 gene in Arabidopsis

• Published in: Molecular biology of the cell Vol. 18; no. 2; pp. 369 - 379
• Main Authors: Pontvianne, Frederic, Matía, Isabel, Douet, Julien, Tourmente, Sylvette, Medina, Francisco J, Echeverria, Manuel, Sáez-Vásquez, Julio
• Format: Journal Article
• Language: English
• Published: United States American Society for Cell Biology 01.02.2007; The American Society for Cell Biology
• Subjects: Amino Acid Sequence; Arabidopsis; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis Proteins; Arabidopsis Proteins - analysis; Arabidopsis Proteins - genetics; Arabidopsis Proteins - physiology; Cell Nucleolus; Cell Nucleolus - chemistry; Cell Nucleolus - metabolism; Cell Nucleolus - ultrastructure; Cell Nucleus; Cell Nucleus - chemistry; DNA, Ribosomal; DNA, Ribosomal - metabolism; Gene Expression Regulation, Plant; Gene Silencing; Genetics; Genome, Plant; Genome, Plant - genetics; Heterochromatin; Heterochromatin - chemistry; Heterochromatin - metabolism; Life Sciences; Molecular Sequence Data; Nuclear Proteins; Nuclear Proteins - analysis; Nuclear Proteins - genetics; Nucleolin; Phosphoproteins; Phosphoproteins - genetics; Phosphoproteins - physiology; Plants genetics; RNA, Ribosomal; RNA, Ribosomal - biosynthesis; RNA-Binding Proteins; RNA-Binding Proteins - analysis; RNA-Binding Proteins - genetics; RNA-Binding Proteins - physiology
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.E06-08-0751

Nucleolin is one of the most abundant protein in the nucleolus and is a multifunctional protein involved in different steps of ribosome biogenesis. In contrast to animals and yeast, the genome of the model plant Arabidopsis thaliana encodes two nucleolin-like proteins, AtNUC-L1 and AtNUC-L2. However, only the AtNUC-L1 gene is ubiquitously expressed in normal growth conditions. Disruption of this AtNUC-L1 gene leads to severe plant growth and development defects. AtNUC-L1 is localized in the nucleolus, mainly in the dense fibrillar component. Absence of this protein in Atnuc-L1 plants induces nucleolar disorganization, nucleolus organizer region decondensation, and affects the accumulation levels of pre-rRNA precursors. Remarkably, in Atnuc-L1 plants the AtNUC-L2 gene is activated, suggesting that AtNUC-L2 might rescue, at least partially, the loss of AtNUC-L1. This work is the first description of a higher eukaryotic organism with a disrupted nucleolin-like gene and defines a new role for nucleolin in nucleolus structure and rDNA chromatin organization.