Ribosomal L1 domain-containing protein 1 coordinates with HDM2 to negatively regulate p53 in human colorectal Cancer cells

Abstract

Background Ribosomal L1 domain-containing protein 1 (RSL1D1) is a nucleolar protein that is essential in cell proliferation. In the current opinion, RSL1D1 translocates to the nucleoplasm under nucleolar stress and inhibits the E3 ligase activity of HDM2 via direct interaction, thereby leading to stabilization of p53. Methods Gene knockdown was achieved in HCT116p53+/+, HCT116p53−/−, and HCT-8 human colorectal cancer (CRC) cells by siRNA transfection. A lentiviral expression system was used to establish cell strains overexpressing genes of interest. The mRNA and protein levels in cells were evaluated by qRT-PCR and western blot analyses. Cell proliferation, cell cycle, and cell apoptosis were determined by MTT, PI staining, and Annexin V-FITC/PI double staining assays, respectively. The level of ubiquitinated p53 protein was assessed by IP. The protein-RNA interaction was investigated by RIP. The subcellular localization of proteins of interest was determined by IFA. Protein-protein interaction was investigated by GST-pulldown, BiFC, and co-IP assays. The therapeutic efficacy of RSL1D1 silencing on tumor growth was evaluated in HCT116 tumor-bearing nude mice. Results RSL1D1 distributed throughout the nucleus in human CRC cells. Silencing of RSL1D1 gene induced cell cycle arrest at G1/S and cell apoptosis in a p53-dependent manner. RSL1D1 directly interacted with and recruited p53 to HDM2 to form a ternary RSL1D1/HDM2/p53 protein complex and thereby enhanced p53 ubiquitination and degradation, leading to a decrease in the protein level of p53. Destruction of the ternary complex increased the level of p53 protein. RSL1D1 also indirectly decreased the protein level of p53 by stabilizing HDM2 mRNA. Consequently, the negative regulation of p53 by RSL1D1 facilitated cell proliferation and survival and downregulation of RSL1D1 remarkably inhibited the growth of HCT116p53+/+ tumors in a nude mouse model. Conclusion We report, for the first time, that RSL1D1 is a novel negative regulator of p53 in human CRC cells and more importantly, a potential molecular target for anticancer drug development.

Single-cell transcriptome analysis reveals heterogeneity and a dynamic regenerative response of quiescent radial glia in adult zebrafish brain

“…Nap1l1 is a nucleosome assembly protein 1-like 1 and promotes cell proliferation of neuronal progenitors and neurogenesis (Qiao et al, 2018). Rsl1d1 is a ribosomal L1 domain-containing 1 that directly interacts with Mdm2 to promote tp53 degradation (Ding et al, 2021). In addition, increased expression of ribosomal proteins such as rps23 and rpl22l2 indicates energy metabolism in qRG1.…”

p53 at the Crossroads between Doxorubicin-Induced Cardiotoxicity and Resistance: A Nutritional Balancing Act

“…Ribosomal L1 structural domain protein 1 (RSL1D1) has been identified as a novel negative regulator of p53 in human colorectal cancer cells. Through direct interaction, it inhibits the E3 ligase activity of HDM2, enhancing the ubiquitination-mediated degradation of p53 and decreasing p53 protein levels [ 94 ]. The oncogene Gankyrin (Gank), a key molecule in hepatoblastoma, induces tumor growth by triggering the degradation of p53 [ 95 ].…”

Programmed cell death 11 modulates but not entirely relies on p53-HDM2 loop to facilitate G2/M transition in colorectal cancer cells

“…It is generally recognized that nucleolar proteins are translocated from the nucleolus to the nucleoplasm in response to nucleolar stress, thereby interacting with and inactivating HDM2, a primary negative regulator of p53, to stabilize p53 protein [1][2][3][4][5]. However, our previous study clarifies a reversed function of nucleolar protein RSL1D1 to increase HDM2-mediated p53 ubiquitination in a cell-type-specific manner [6]. Other than its nucleolus-specific localization in normal cells or other types of cancer cells [5,7,8], RSL1D1 is overexpressed and colocalized with p53 and HDM2 throughout the nucleus of HCT116 colorectal cancer (CRC) cells [6].…”