Noncoding RNAs and the control of signalling via nuclear receptor regulation in health and disease.

Nuclear receptors belong to a superfamily of proteins that play central roles in human biology, orchestrating a large variety of biological functions in both health and disease. Understanding the interactions and regulatory pathways of NRs will allow development of potential therapeutic interventions for a multitude of disease processes. Non-coding RNAs have recently been discovered to have significant interactions with NR signalling pathways via a variety of biological connections. This review summarises the known interactions between ncRNAs and the NR superfamily in health, embryogenesis and a plethora of human diseases.

C-terminal region of EBNA-2 determines the superior transforming ability of type 1 Epstein-Barr virus by enhanced gene regulation of LMP-1 and CXCR7.

Type 1 Epstein-Barr virus (EBV) strains immortalize B lymphocytes in vitro much more efficiently than type 2 EBV, a difference previously mapped to the EBNA-2 locus. Here we demonstrate that the greater transforming activity of type 1 EBV correlates with a stronger and more rapid induction of the viral oncogene LMP-1 and the cell gene CXCR7 (which are both required for proliferation of EBV-LCLs) during infection of primary B cells with recombinant viruses. Surprisingly, although the major sequence differences between type 1 and type 2 EBNA-2 lie in N-terminal parts of the protein, the superior ability of type 1 EBNA-2 to induce proliferation of EBV-infected lymphoblasts is mostly determined by the C-terminus of EBNA-2. Substitution of the C-terminus of type 1 EBNA-2 into the type 2 protein is sufficient to confer a type 1 growth phenotype and type 1 expression levels of LMP-1 and CXCR7 in an EREB2.5 cell growth assay. Within this region, the RG, CR7 and TAD domains are the minimum type 1 sequences required. Sequencing the C-terminus of EBNA-2 from additional EBV isolates showed high sequence identity within type 1 isolates or within type 2 isolates, indicating that the functional differences mapped are typical of EBV type sequences. The results indicate that the C-terminus of EBNA-2 accounts for the greater ability of type 1 EBV to promote B cell proliferation, through mechanisms that include higher induction of genes (LMP-1 and CXCR7) required for proliferation and survival of EBV-LCLs.

The estrogen receptor-alpha-induced microRNA signature regulates itself and its transcriptional response.

Following estrogenic activation, the estrogen receptor-alpha (ERalpha) directly regulates the transcription of target genes via DNA binding. MicroRNAs (miRNAs) modulated by ERalpha have the potential to fine tune these regulatory systems and also provide an alternate mechanism that could impact on estrogen-dependent developmental and pathological systems. Through a microarray approach, we identify the subset of microRNAs (miRNAs) modulated by ERalpha, which include upregulation of miRNAs derived from the processing of the paralogous primary transcripts (pri-) mir-17-92 and mir-106a-363. Characterization of the mir-17-92 locus confirms that the ERalpha target protein c-MYC binds its promoter in an estrogen-dependent manner. We observe that levels of pri-mir-17-92 increase earlier than the mature miRNAs derived from it, implicating precursor cleavage modulation after transcription. Pri-mir-17-92 is immediately cleaved by DROSHA to pre-miR-18a, indicating that its regulation occurs during the formation of the mature molecule from the precursor. The clinical implications of this novel regulatory system were confirmed by demonstrating that pre-miR-18a was significantly upregulated in ERalpha-positive compared to ERalpha-negative breast cancers. Mechanistically, miRNAs derived from these paralogous pri-miRNAs (miR-18a, miR-19b, and miR-20b) target and downregulate ERalpha, while a subset of pri-miRNA-derived miRNAs inhibit protein translation of the ERalpha transcriptional p160 coactivator, AIB1. Therefore, different subsets of miRNAs identified act as part of a negative autoregulatory feedback loop. We propose that ERalpha, c-MYC, and miRNA transcriptional programs invoke a sophisticated network of interactions able to provide the wide range of coordinated cellular responses to estrogen.

Differential gene regulation by Epstein-Barr virus type 1 and type 2 EBNA2.

A transfection assay with a lymphoblastoid cell line infected with Epstein-Barr virus was used to compare the abilities of type 1 and type 2 EBNA2 to sustain cell proliferation. The reduced proliferation in cells expressing type 2 EBNA2 correlated with loss of expression of some cell genes that are known to be targets of type 1 EBNA2. Microarray analysis of EBNA2 target genes identified a small number of genes that are more strongly induced by type 1 than by type 2 EBNA2, and one of these genes (CXCR7) was shown to be required for proliferation of lymphoblastoid cell lines. The Epstein-Barr virus LMP1 gene was also more strongly induced by type 1 EBNA2 than by type 2, but this effect was transient. Type 1 and type 2 EBNA2 were equally effective at arresting cell proliferation of Burkitt's lymphoma cell lines lacking Epstein-Barr virus and were also shown to cause apoptosis in these cells. The results indicate that differential gene regulation by Epstein-Barr virus type 1 and type 2 EBNA2 may be the basis for the much weaker B-cell transformation activity of type 2 Epstein-Barr virus strains compared to type 1 strains.

Cell target genes of Epstein-Barr virus transcription factor EBNA-2: induction of the p55alpha regulatory subunit of PI3-kinase and its role in survival of EREB2.5 cells.

Microarray analysis covering most of the annotated RNAs in the human genome identified a panel of genes induced by the Epstein-Barr virus (EBV) EBNA-2 transcription factor in the EREB2.5 human B-lymphoblastoid cell line without the need for any intermediate protein synthesis. Previous data indicating that PIK3R1 RNA (the alpha regulatory subunit of PI3-kinase) was induced were confirmed, but it is now shown that it is the p55alpha regulatory subunit that is induced. Several EBV-immortalized lymphoblastoid cell lines were shown to express p55alpha. Expression of PI3-kinase p85 regulatory and p110 catalytic subunits was not regulated by EBNA-2. Proliferation of EREB2.5 lymphoblastoid cells was inhibited by RNAi knock-down of p55alpha protein expression, loss of p55alpha being accompanied by an increase in apoptosis. p55alpha is thus a functional target of EBNA2 in EREB2.5 cells and the specific regulation of p55alpha by EBV will provide an opportunity to investigate the physiological function of p55alpha in this human cell line.