Involvement of S-cerevisiae Rpb4 in subset of pathways related to transcription elongation

Yeast Rpb4, a subunit of RNA pol II is not essential for viability but is involved in multiple cellular phenotypes such as temperature sensitivity, enhanced pseudohyphal morphology, and decreased sporulation. Both in vivo and in vitro studies strongly support involvement of Rpb4 in transcription initiation, while its role in transcription elongation is not entirely consistent. Here we show that Rpb4 is not required for recruitment of RNA pol II on the coding region of YLR454w, a representative long gene. Yet we find strong genetic interaction of rpb4 Delta with mutants in many transcription elongation factors such as Paf1, Spt4, Dst1, Elp3 and Rpb9. We demonstrate that, Rpb4 interacts functionally with Paf1 to affect the transcription elongation of the FKS1 gene. Our results suggest that while Rpb4 is not required for general transcription elongation, it could support transcription elongation for specific of class of genes by interaction with other elongation factors. (C) 2014 Elsevier B.V. All rights reserved.

MicroRNA-125a Reduces Proliferation and Invasion of Oral Squamous Cell Carcinoma Cells by Targeting Estrogen-related Receptor alpha IMPLICATIONS FOR CANCER THERAPEUTICS

Estrogen-related receptor (ESRRA) functions as a transcription factor and regulates the expression of several genes, such as WNT11 and OPN. Up-regulation of ESRRA has been reported in several cancers. However, the mechanism underlying its up-regulation is unclear. Furthermore, the reports regarding the role and regulation of ESRRA in oral squamous cell carcinoma (OSCC) are completely lacking. Here, we show that tumor suppressor miR-125a directly binds to the 3UTR of ESRRA and represses its expression. Overexpression of miR-125a in OSCC cells drastically reduced the level of ESRRA, decreased cell proliferation, and increased apoptosis. Conversely, the delivery of an miR-125a inhibitor to these cells drastically increased the level of ESRRA, increased cell proliferation, and decreased apoptosis. miR-125a-mediated down-regulation of ESRRA impaired anchorage-independent colony formation and invasion of OSCC cells. Reduced cell proliferation and increased apoptosis of OSCC cells were dependent on the presence of the 3UTR in ESRRA. The delivery of an miR-125a mimic to OSCC cells resulted in marked regression of xenografts in nude mice, whereas the delivery of an miR-125a inhibitor to OSCC cells resulted in a significant increase of xenografts and abrogated the tumor suppressor function of miR-125a. We observed an inverse correlation between the expression levels of miR-125a and ESRRA in OSCC samples. In summary, up-regulation of ESRRA due to down-regulation of miR-125a is not only a novel mechanism for its up-regulation in OSCC, but decreasing the level of ESRRA by using a synthetic miR-125a mimic may have an important role in therapeutic intervention of OSCC and other cancers.

Genomic amplification upregulates estrogen-related receptor alpha and its depletion inhibits oral squamous cell carcinoma tumors in vivo

The ESRRA gene encodes a transcription factor and regulates several genes, such as WNT11 and OPN, involved in tumorigenesis. It is upregulated in several cancers, including OSCC. We have previously shown that the tumor suppressor miR-125a targets ESRRA, and its downregulation causes upregulation of ESRRA in OSCC. Upregulation of ESRRA in the absence of downregulation of miR-125a in a subset of OSCC samples suggests the involvement of an alternative mechanism. Using TaqMan (R) copy number assay, here we report for the first time that the genomic amplification of ESRRA causes its upregulation in a subset of OSCC samples. Ectopic overexpression of ESRRA led to accelerated cell proliferation, anchorage-independent cell growth and invasion, and inhibited apoptosis. Whereas, knockdown of ESRRA expression by siRNA led to reduced cell proliferation, anchorage-independent cell growth and invasion, and accelerated apoptosis. Furthermore, the delivery of a synthetic biostable ESRRA siRNA to OSCC cells resulted in regression of xenografts in nude mice. Thus, the genomic amplification of ESRRA is another novel mechanism for its upregulation in OSCC. Based on our in vitro and in vivo experiments, we suggest that targeting ESRRA by siRNA could be a novel therapeutic strategy for OSCC and other cancers.