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Background/objectives: Nucleolin is a major component of the nucleolus and is involved in various aspects of ribosome biogenesis. However, it is also implicated in non-nucleolar functions such as cell cycle regulation and proliferation, linking it to various pathologic processes. The aim of this study was to use differential gene expression analysis and Weighted Gene Co-expression Network analysis (WGCNA) to identify nucleolin-related regulatory pathways and possible key genes as novel therapeutic targets for cancer, viral infections and other diseases. Methods: We used two different siRNAs to downregulate the expression of nucleolin in a human hepatoblastoma (HepG2) cell line. We carried out RNA-sequencing (RNA-Seq), performed enrichment analysis of the pathways of the differentially expressed genes (DEGs) and identified protein–protein interaction (PPI) networks. Results: Both siRNAs showed high knockdown efficiency in HepG2 cells, resulting in the disruption of the nucleolar architecture and the downregulation of rRNA gene expression, both downstream hallmarks of a loss of nucleolin function. RNA-Seq identified 44 robust DEGs in both siRNA cell models. The enrichment analysis of the pathways of the downregulated genes confirmed the essential role of nucleolin in DNA replication and cell cycle processes. In addition, we identified seven hub genes linked to NCL: MCM6, MCM3, FEN1, MYBL2, MSH6, CDC6 and RBM14; all are known to be implicated in DNA replication, cell cycle progression and oncogenesis. Conclusions: Our findings demonstrate the functional consequences of nucleolin depletion in HepG2 and confirm the importance of nucleolin in DNA replication and cell cycle processes. These data will further enhance our understanding of the molecular and pathologic mechanisms of nucleolin and provide new therapeutic perspectives in disease. [ABSTRACT FROM AUTHOR]

The intrinsically disordered protein MeCP2 is a global transcriptional regulator encoded by the MECP2 gene. Although the structured domains of MeCP2 have been the subject of multiple studies, its unstructured regions have not been that extensively characterized. In this work, we show that MeCP2 possesses properties akin to those of supercharged proteins. By utilizing its unstructured portions, MeCP2 can successfully transduce across cell membranes and localize to heterochromatic foci in the nuclei, displaying uptake levels a third lower than a MeCP2 construct fused to the cell‐penetrating peptide TAT. MeCP2 uptake can further be enhanced by the addition of compounds that promote endosomal escape following cellular trafficking by means of macropinocytosis. Using a combination of in silico prediction algorithms and live‐cell imaging experiments, we mapped the sequence in MeCP2 responsible for its cellular incorporation, which bears a striking resemblance to TAT itself. Transduced MeCP2 was shown to interact with HDAC3. These findings provide valuable insight into the properties of MeCP2 and may be beneficial for devising future protein‐based treatment strategies. [ABSTRACT FROM AUTHOR]

The intrinsically disordered protein MeCP2 is a global transcriptional regulator encoded by the MECP2 gene. Although the structured domains of MeCP2 have been the subject of multiple studies, its unstructured regions have not been that extensively characterized. In this work, we show that MeCP2 possesses properties akin to those of supercharged proteins. By utilizing its unstructured portions, MeCP2 can successfully transduce across cell membranes and localize to heterochromatic foci in the nuclei, displaying uptake levels a third lower than a MeCP2 construct fused to the cell-penetrating peptide TAT. MeCP2 uptake can further be enhanced by the addition of compounds that promote endosomal escape following cellular trafficking by means of macropinocytosis. Using a combination of in silico prediction algorithms and live-cell imaging experiments, we mapped the sequence in MeCP2 responsible for its cellular incorporation, which bears a striking resemblance to TAT itself. Transduced MeCP2 was shown to interact with HDAC3. These findings provide valuable insight into the properties of MeCP2 and may be beneficial for devising future protein-based treatment strategies., (© 2024 The Author(s). Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.)

Structural features and internal dynamics of inosine-containing RNAs are poorly understood. NMR studies of such RNAs require 13 C, 15 N-labeling, which cannot be achieved using in vitro transcription as inosine and guanosine are not distinguished by RNA polymerase. Herein, we report the synthesis of an inosine phosphoramidite with selective 13 C8 and 15 N7-isotope incorporation in the base and uniform 13 C-labeling of the ribose. Chemical synthesis of an RNA duplex containing four consecutive IU base pairs with this optimized isotope-labeling scheme greatly simplifies NMR spectra and resolves signal overlap. The absence of detectable NMR signals of imino protons and unusual inter-residue NOE correlations in this RNA indicate deviations from standard A-form geometry, consistent with reduced stability of this duplex seen in UV melting studies compared to its nonedited RNA counterparts. These studies indicate that the introduction of IU base pairs distorts and destabilizes RNA helices significantly compared to the also noncanonical GU base-pairs. Our optimized isotope-labeling scheme enables high-resolution NMR studies of inosine-edited RNAs., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)