Nucleolin is required for DNA methylation state and the expression of rRNA gene variants in Arabidopsis thaliana.
In eukaryotes, 45S rRNA genes are arranged in tandem arrays in copy numbers ranging from several hundred to several thousand in plants. Although it is clear that not all copies are transcribed under normal growth conditions, the molecular basis controlling the expression of specific sets of rRNA genes remains unclear. Here, we report four major rRNA gene variants in Arabidopsis thaliana. Interestingly, while transcription of one of these rRNA variants is induced, the others are either repressed or remain unaltered in A. thaliana plants with a disrupted nucleolin-like protein gene (Atnuc-L1). Remarkably, the most highly represented rRNA gene variant, which is inactive in WT plants, is reactivated in Atnuc-L1 mutants. We show that accumulated pre-rRNAs originate from RNA Pol I transcription and are processed accurately. Moreover, we show that disruption of the AtNUC-L1 gene induces loss of symmetrical DNA methylation without affecting histone epigenetic marks at rRNA genes. Collectively, these data reveal a novel mechanism for rRNA gene transcriptional regulation in which the nucleolin protein plays a major role in controlling active and repressed rRNA gene variants in Arabidopsis.
UMR 5096 CNRS-IRD-University de Perpignan, Perpignan, France.
Frédéric
F
Pontvianne
Mohamed
M
Abou-Ellail
Julien
J
Douet
Pascale
P
Comella
Isabel
I
Matia
Chinmayi
C
Chandrasekhara
Anne
A
Debures
Todd
T
Blevins
Richard
R
Cooke
Francisco J
FJ
Medina
Sylvette
S
Tourmente
Craig S
CS
Pikaard
Julio
J
Sáez-Vásquez
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D019175:DNA Methylation / Q000235:genetics*; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020459:Genes, rRNA / Q000235:genetics*; D006657:Histones / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D009697:Nucleolus Organizer Region / Q000235:genetics; D009707:Nucleosomes / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012318:RNA Polymerase I / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D014158:Transcription, Genetic; D000097796:Nucleolin
D029681:Arabidopsis Proteins; D021903:DNA, Ribosomal Spacer; D006657:Histones; D009707:Nucleosomes; D010750:Phosphoproteins; D012318:RNA Polymerase I; D018749:RNA, Plant; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D000097796:Nucleolin; C519187:NUC-L1 protein, Arabidopsis; C088179:RNA, ribosomal, 45S