Subcellular localization of p44/WDR77 determines proliferation and differentiation of prostate epithelial cells

Molecular cloning, characterization, and gene expression behavior of glucocorticoid and mineralocorticoid receptors from the Chinese alligator (Alligator sinensis)

The Chinese alligator is an endemic crocodilian species in China. We isolated and obtained the glucocorticoid and mineralocorticoid receptor genes coding from the kidney of Alligator sinensis by nested polymerase chain reaction (PCR) and rapid amplification of cDNA ends (RACE). The glucocorticoid receptor (GR) gene has 2343 base pairs encoding 780 amino acids, while the mineralocorticoid receptor (MR) gene is 2958 bp in length encoding 985 amino acids. Quantitative real-time PCR was used to detect the distribution of messenger RNA (mRNA) levels. The maximum mRNA expressions were observed in the ovary and kidney, suggesting that these receptors may be involved in basic cellular functions or stress response of alligators. Besides this, RT-qPCR was performed to analyze the abundance of GR and MR mRNA transcripts in early embryonic development of the Chinese alligator in the kidney, liver, and heart. The mRNA levels of GR and MR at earlier stages in kidney, liver, and heart indicates that they might involve in the transcriptional regulation of early embryos and activate many precise developmental effects in fetal tissues. We also measured the protein expression in the liver embryonic developmental stages and found that the GR and MR proteins were restricted to both the nuclei and cytoplasm. The protein expression levels in the liver at different embryonic developmental stages have extremely prominent differences. Taken together, our results showed the full coding regions of GR and MR, their characteristics, and embryonic developmental mRNA and protein expressions of both genes in A. sinensis. This study could provide the necessary information for further investigating the diverse functions of GR and MR in A. sinensis.

WD Repeat Domain 77 Protein Regulates Translation of E2F1 and E2F3 mRNA

WD repeat domain 77 protein (WDR77) is required for cellular proliferation of lung and prostate epithelial cells during earlier stages of development and is reactivated during prostate and lung tumorigenesis. WDR77 plays an essential role in prostate tumorigenesis and cell growth mediated by growth regulatory factors. Here, we identified E2F1 and E2F3 mRNAs as translational targets of WDR77. We demonstrated that WDR77 regulated the translation of E2F1 and E2F3 mRNAs through the 5' untranslated regions (UTRs) of E2F1 and E2F3 (E2F1/3) mRNAs. WDR77 physically interacted with programmed cell death 4 (PDCD4) that suppresses translation of mRNAs containing structured 5' UTRs by interacting with eukaryotic translation initiation factor 4A (eIF4A) and inhibiting its helicase activity. Further, we demonstrated that the interaction between WDR77 and PDCD4 prevented the binding of PDCD4 to eIF4A and relieved PDCD4's inhibitory effect on eIF4A1. Overall, our work reveals for the first time that WDR77 is directly involved in translational regulation of E2F1/3 mRNAs through their structured 5' UTRs, PDCD4, and eIF4A1 and provides novel insight into the cell growth controlled by WDR77.

Molecular cloning, characterization, mRNA expression changes and nucleocytoplasmic shuttling during kidney embryonic development of SOX9 in Alligator sinensis

SOX9 plays a crucial, extensive and conservative role in the process of somatic tissue development and adult regeneration through the positive self-regulation mediated by SOM across all vertebrates. In this study, we have cloned SOX9 from the kidney of hatchling Alligator sinensis. The full-length of SOX9 cDNA is 3878 bp with an open reading frame encoding 494 amino acids. Amino acid alignment analyses indicated that the SOX9 exhibit highly conserved functional domains. Using the droplet digital PCR, the mRNA abundances of SOX9 during nephrogenesis in A. sinensis showed prominent changes in the embryonic development, suggesting that SOX9 might combines a vital role in the regulation of complex renal development. Interestingly, we detected the nucleocytoplasmic shuttling of SOX9 protein using immunofluorescence, implying that nucleocytoplasmic shuttling is critical to the regulation of SOX9 in the renal embryonic development. Collectively, these data provide an important foundation for further studies on renal developmental biology and molecular biology of non-mammalian SOX9. Furthermore, it provides new insights into the phenomenon of SOX9 nucleocytoplasmic shuttling in Alligator sinensis, which is probably of great significance to the development of kidney metanephros embryo.

The essential role of WD repeat domain 77 in prostate tumor initiation induced by Pten loss

Prostate cancer is the most commonly diagnosed malignancy among men, but few genetic factors that drive prostate cancer initiation have been identified. The WD repeat domain 77 (Wdr77) protein is essential for cellular proliferation when localizes in the cytoplasm of epithelial cells at the early stage of prostate development. In the adult prostate, it is transported into the nucleus and functions as a co-regulator of the androgen receptor to promote cellular differentiation and prostate function. This developmental process is reversed during prostate tumorigenesis, i.e., Wdr77 is translocated from the nucleus into the cytoplasm to drive proliferation of prostate cancer cells. In this study, we used in vivo genetic studies to further investigate the role of Wdr77 in prostate tumorigenesis. We found that prostate-specific deletion of Wdr77 abolished prostate tumor initiation induced by loss of the tumor suppressor Pten. Mechanistically, Wdr77 ablation inhibited E2F3 activation and enhanced TGFβ signaling, leading to attenuated cellular proliferation induced by loss of Pten. These findings establish a critical role of Wdr77 for prostate tumor initiation.

The Structure and Function of the PRMT5:MEP50 Complex

Protein arginine methyltransferase 5 (PRMT5) plays multiple roles in cellular processes at different stages of the cell cycle in a tissue specific manner. PRMT5 in complex with MEP50/p44/WDR77 associates with a plethora of partner proteins to symmetrically dimethylate arginine residues on target proteins in both the nucleus and the cytoplasm. Overexpression of PRMT5 has been observed in several cancers, making it an attractive drug target. The structure of the 453 kDa heterooctameric PRMT5:MEP50 complex bound to an S-adenosylmethionine analog and a substrate peptide provides valuable insights into this intriguing target.

Protein arginine methyltransferase 5 regulates multiple signaling pathways to promote lung cancer cell proliferation

BACKGROUND

Protein arginine methyltransferase 5 (PRMT5) catalyzes the formation of symmetrical dimethylation of arginine residues in proteins. WD repeat domain 77 (WDR77), also known as p44, MEP50, or WD45, forms a stoichiometric complex with PRMT5. The PRMT5/p44 complex is required for cellular proliferation of lung and prostate epithelial cells during earlier stages of development and is re-activated during prostate and lung tumorigenesis. The molecular mechanisms by which PRMT5 and p44 promote cellular proliferation are unknown.

METHODS

Expression of PRMT5 and p44 in lung and prostate cancer cells was silenced and their target genes were identified. The regulation of target genes was validated in various cancer cells during lung development and tumorigenesis. Altered expression of target genes was achieved by ectopic cDNA expression and shRNA-mediated silencing.

RESULTS

PRMT5 and p44 regulate expression of a specific set of genes encoding growth and anti-growth factors, including receptor tyrosine kinases and antiproliferative proteins. Genes whose expression was suppressed by PRMT5 and p44 encoded anti-growth factors and inhibited cell growth when ectopically expressed. In contrast, genes whose expression was enhanced by PRMT5 and p44 encoded growth factors and increased cell growth when expressed. Altered expression of target genes is associated with re-activation of PRMT5 and p44 during lung tumorigenesis.

CONCLUSIONS

Our data provide the molecular basis by which PRMT5 and p44 regulate cell growth and lay a foundation for further investigation of their role in lung tumor initiation.

Yeast two-hybrid screening identified WDR77 as a novel interacting partner of TSC22D2

Transforming growth factor β-stimulated clone 22 domain family, member 2 (TSC22D2), a member of the TSC22D family, has been implicated as a tumor-associated gene, but its function remains unknown. To further explore its biological role, yeast two-hybrid screening combined with multiple bioinformatics tools was used to identify 44 potential interacting partners of the TSC22D2 protein that were mainly involved in gene transcription, cellular metabolism, and cell cycle regulation. The protein WD repeat domain 77 (WDR77) was selected for further validation due to its function in the cell cycle and tumor development, as well as its high detection frequency in the yeast two-hybrid assay. Immunoprecipitation and immunofluorescence experiments confirmed an interaction between the TSC22D2 and WDR77 proteins. Our work greatly expands the putative protein interaction network of TSC22D2 and provides deeper insight into the biological functions of the TSC22D2 and WDR77 proteins.

E2F and GATA switches turn off WD repeat domain 77 expression in differentiating cells

WDR77 (WD repeat domain 77) is expressed during earlier lung development when cells are rapidly proliferating, but is absent from adult lung. It is re-activated during lung tumorigenesis and is essential for lung cancer cell proliferation. Signalling pathways/molecules that control WDR77 gene expression are unknown. Promoter mapping, gel shift assay and ChIP revealed that the WDR77 promoter contains bona fide response elements for E2F and GATA transcriptional factors as demonstrated in prostate cancer, lung cancer and erythroid cells, as well as in mouse lung tissues. The WDR77 promoter is transactivated by E2F1, E2F3, GATA1 and GATA6, but suppressed by E2F6, GATA1 and GATA3 in prostate cancer PC3 cells. WDR77 expression is associated with E2F1, E2F3, GATA2 and GATA6 occupancy on the WDR77 gene, whereas, in contrast, E2F6, GATA1 and GATA3 occupancy is associated with the loss of WDR77 expression during erythroid maturation and lung development. More importantly, the loss of WDR77 expression that results from E2F and GATA switches is required for cellular differentiation of erythroid and lung epithelial cells. In contrast, lung cancer cells avoid post-mitotic differentiation by sustaining WDR77 expression. Altogether, the present study provides a novel molecular mechanism by which WDR77 is regulated during erythroid and lung development and lung tumorigenesis.

GLI pathogenesis-related 1 functions as a tumor-suppressor in lung cancer

Background

GLI pathogenesis-related 1 (GLIPR1) was originally identified in glioblastomas and its expression was also found to be down-regulated in prostate cancer. Functional studies revealed both growth suppression and proapoptotic activities for GLIPR1 in multiple cancer cell lines. GLIPR1’s role in lung cancer has not been investigated. Protein arginine methyltransferase 5 (PRMT5) is a protein arginine methyltransferase and forms a stoichiometric complex with the WD repeat domain 77 (WDR77) protein. Both PRMT5 and WDR77 are essential for growth of lung epithelial and cancer cells. But additional gene products that interact genetically or biochemichally with PRMT5 and WDR77 in the control of lung cancer cell growth are not characterized.

Methods

DNA microarray and immunostaining were used to detect GLIPR1 expression during lung development and lung tumorigenesis. GLIPR1 expression was also analyzed in the TCGA lung cancer cohort. The consequence of GLIPR1 on growth of lung cancer cells in the tissue culture and lung tumor xenografts in the nude mice was observed.

Results

We found that GLIPR1 expression is negatively associated with PRMT5/WDR77. GLIPR1 is absent in growing epithelial cells at the early stages of mouse lung development and highly expressed in the adult lung. Expression of GLIPR1 was down-regulated during lung tumorigenesis and its expression suppressed growth of lung cancer cells in the tissue culture and lung tumor xenografts in mice. GLIPR1 regulates lung cancer growth through the V-Erb-B avian erythroblastic leukemia viral oncogene homolog 3 (ErbB3).

Conclusions

This study reveals a novel pathway that PRMT5/WDR77 regulates GLIPR1 expression to control lung cancer cell growth and GLIPR1 as a potential therapeutic agent for lung cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0508-4) contains supplementary material, which is available to authorized users.

The PRMT5 arginine methyltransferase: many roles in development, cancer and beyond

Post-translational arginine methylation is responsible for regulation of many biological processes. The protein arginine methyltransferase 5 (PRMT5, also known as Hsl7, Jbp1, Skb1, Capsuleen, or Dart5) is the major enzyme responsible for mono- and symmetric dimethylation of arginine. An expanding literature demonstrates its critical biological function in a wide range of cellular processes. Histone and other protein methylation by PRMT5 regulate genome organization, transcription, stem cells, primordial germ cells, differentiation, the cell cycle, and spliceosome assembly. Metazoan PRMT5 is found in complex with the WD-repeat protein MEP50 (also known as Wdr77, androgen receptor coactivator p44, or Valois). PRMT5 also directly associates with a range of other protein factors, including pICln, Menin, CoPR5 and RioK1 that may alter its subcellular localization and protein substrate selection. Protein substrate and PRMT5-MEP50 post-translation modifications induce crosstalk to regulate PRMT5 activity. Crystal structures of C. elegans PRMT5 and human and frog PRMT5-MEP50 complexes provide substantial insight into the mechanisms of substrate recognition and procession to dimethylation. Enzymological studies of PRMT5 have uncovered compelling insights essential for future development of specific PRMT5 inhibitors. In addition, newly accumulating evidence implicates PRMT5 and MEP50 expression levels and their methyltransferase activity in cancer tumorigenesis, and, significantly, as markers of poor clinical outcome, marking them as potential oncogenes. Here, we review the substantial new literature on PRMT5 and its partners to highlight the significance of understanding this essential enzyme in health and disease.

P44/WDR77 restricts the sensitivity of proliferating cells to TGFβ signaling

We previously reported that a novel WD-40 domain-containing protein, p44/WDR77, drives quiescent epithelial cells to re-enter the cell cycle and plays an essential role for growth of lung and prostate cancer cells. Transforming growth factor beta (TGFβ) signaling is important in the maintenance of non-transformed cells in the quiescent or slowly cycling stage. However, both non-transformed proliferating cells and human cancer cells are non-responsive to endogenous TGFβ signaling. The mechanism by which proliferating cells become refractory to TGFβ inhibition is not well established. Here, we found that silencing p44/WDR77 increased cellular sensitivity to TGFβ signaling and that this was inversely correlated with decreased cell proliferation. Smad2 or 3 phosphorylation, TGFβ-mediated transcription, and TGFβ2 and TGFβ receptor type II (TβRII) expression were dramatically induced by silencing of p44/WDR77. These data support the hypothesis that p44/WDR77 down-regulates the expression of the TGFβ ligand and its receptor, thereby leading to a cellular non-response to TGFβ signaling. Finally, we found that p44/WDR77 expression was correlated with cell proliferation and decreased TGFβ signaling during lung tumorigenesis. Together, these results suggest that p44/WDR77 expression causes the non-sensitivity of proliferating cells to TGFβ signaling, thereby contributing to cellular proliferation during lung tumorigenesis.