Chromatin tethering effects of hNopp140 are involved in the spatial organization of nucleolus and the rRNA gene transcription

Abstract

The short arms of five human acrocentric chromosomes contain ribosomal gene (rDNA) clusters where numerous mini-nucleoli arise at the exit of mitosis. These small nucleoli tend to coalesce into one or a few large nucleoli during interphase by unknown mechanisms. Here, we demonstrate that the N-and C-terminal domains of a nucleolar protein, hNopp140, bound respectively to a-satellite arrays and rDNA clusters of acrocentric chromosomes for nucleolar formation. The central acidicand-basic repeated domain of hNopp140, possessing a weak self-self interacting ability, was indispensable for hNopp140 to build up a nucleolar round-shaped structure. The N-or the C-terminally truncated hNopp140 caused nucleolar segregation and was able to alter locations of the rDNA transcription, as mediated by detaching the rDNA repeats from the acrocentric a-satellite arrays. Interestingly, an hNopp140 mutant, made by joining the N-and C-terminal domains but excluding the entire central repeated region, induced nucleolar disruption and global chromatin condensation. Furthermore, RNAi knockdown of hNopp140 resulted in dispersion of the rDNA and acrocentric a-satellite sequences away from nucleolus that was accompanied by rDNA transcriptional silence. Our findings indicate that hNopp140, a scaffold protein, is involved in the nucleolar assembly, fusion, and maintenance.

GM1 Ganglioside is Involved in Epigenetic Activation Loci of Neuronal Cells

“…The sequences of the primer pair are: 5’-TTT GGG GAC GAA GGG ATG TG-3’; 5’-GAC TCC GGG GCT TTG TAG AC-3’. Procedures for in-situ hybridization were as previously described [36]. The genomic DNA targeted by the probe was revealed by an anti-digoxigenin antibody (Roche; clone 1.71.256; mouse IgG1) (1:500 dilution in 1% BSA/PBS) followed by Alexa Fluo-conjugated secondary antibody.…”

Identification of nucleolar and coiled-body phosphoprotein 1 (NOLC1) minimal promoter regulated by NF-κB and CREB

“…NOLC1 rapidly shuttles between the nucleus and the cytoplasm, perhaps to facilitate the import of nucleolar ribosome assembly factors or the export of nucleolar products. Knockdown of NOLC1 blocks pre-rRNA synthesis (9), and NOLC1 may also play a role in the maintenance of nucleolar integrity. When an exogenous NOLC1 N-terminus is expressed, cell nucleoli structures become altered, mislocalize the endogenous Pol I and shut off cellular rRNA gene transcription.…”

Vectors for co-expression of two genes in Caenorhabditis elegans

“…Furthermore, some DsRedLD signals did not perfectly co-localize in the nucleoli of the intestine cells but appeared to protrude at the edge of the nucleolus (Figs. 2F and G) in a way similar to the over-expression pattern of the nucleolus protein, Nopp140, in HeLa cells (Tsai et al, 2008).…”