Pseudogenes: A Novel Source of Trans-Acting Antisense RNAs

PTEN, PTENP1, microRNAs, and ceRNA Networks: Precision Targeting in Cancer Therapeutics

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a well characterised tumour suppressor, playing a critical role in the maintenance of fundamental cellular processes including cell proliferation, migration, metabolism, and survival. Subtle decreases in cellular levels of PTEN result in the development and progression of cancer, hence there is tight regulation of the expression, activity, and cellular half-life of PTEN at the transcriptional, post-transcriptional, and post-translational levels. PTENP1, the processed pseudogene of PTEN, is an important transcriptional and post-transcriptional regulator of PTEN. PTENP1 expression produces sense and antisense transcripts modulating PTEN expression, in conjunction with miRNAs. Due to the high sequence similarity between PTEN and the PTENP1 sense transcript, the transcripts possess common miRNA binding sites with the potential for PTENP1 to compete for the binding, or 'sponging', of miRNAs that would otherwise target the PTEN transcript. PTENP1 therefore acts as a competitive endogenous RNA (ceRNA), competing with PTEN for the binding of specific miRNAs to alter the abundance of PTEN. Transcription from the antisense strand produces two functionally independent isoforms (PTENP1-AS-α and PTENP1-AS-β), which can regulate PTEN transcription. In this review, we provide an overview of the post-transcriptional regulation of PTEN through interaction with its pseudogene, the cellular miRNA milieu and operation of the ceRNA network. Furthermore, its importance in maintaining cellular integrity and how disruption of this PTEN-miRNA-PTENP1 axis may lead to cancer but also provide novel therapeutic opportunities, is discussed. Precision targeting of PTENP1-miRNA mediated regulation of PTEN may present as a viable alternative therapy.

Pseudogene SNRPFP1 derived long non-coding RNA facilitates hepatocellular carcinoma progress in vitro by sponging tumor-suppressive miR-126-5p

Pseudogene-derived transcripts, especially those barely transcribed in normal tissues, have been regarded as a kind of non-coding RNAs, and present potential functions in tumorigenicity and tumor development in human beings. However, their exact effects on hepatocellular carcinoma (HCC) remain largely unknown. On basis of our previous research and the constructed online database for the non-coding RNAs related to HCC, a series of pseudogene transcripts have been discovered, and SNRPFP1, the homologous pseudogene of SNRPF, was found to produce an anomalously high expression long non-coding RNA in HCC. In this study, we validated the expression of the SNRPFP1 transcript in both HCC tissues and cell lines. The adverse correlation between SNRPFP1 expression and patients' outcomes was observed. And depletion of SNRPF1 in HCC cells significantly suppressed cell proliferation and apoptosis resistance. Meanwhile, the motility of HCC cells was potently impaired. Interestingly, miR-126-5p, one of the tumor-suppressive genes commonly decreased in HCC, was found negatively expressed and correlated with SNRPF1, and a specific region of SNRPF1 transcript is directly binding to miR-126-5p in a molecular sponge way. The rescue experiment by knock-out miR-126-5p significantly reversed the cell growth suppression and a higher ratio of cell apoptosis induced by SNRPF1 depletion. Lastly, we concluded that SNRPF1 is a pseudogene active in HCC, and its abnormally over-expressed transcript is a strong promoter of HCC cell progress in vitro by sponging miR-126-5p. We believe that the findings in this study provide new strategies for HCC prevention and therapeutic treatment.

Pseudogene UBE2MP1 derived transcript enhances in vitro cell proliferation and apoptosis resistance of hepatocellular carcinoma cells through miR-145-5p/RGS3 axis

Pseudogenes are barely transcribed at normal, while the anomalous transcripts of them are mostly regarded as long non-coding RNAs (lncRNAs), which play potential functions in human tumorigenicity and development. The exact effects of pseudogene-derived transcripts on hepatocellular carcinoma (HCC) are ambiguous. According to our previous research and constructed database on the HCC-related lncRNAs, we noticed that UBE2MP1 was transcriptionally activated in HCC as a pseudogene from the ubiquitin-conjugating enzyme member UBE2M. In this study, we validated the high expression of the UBE2MP1 transcript in HCC and its adverse correlation with dismal outcomes for the patients. UBE2MP1 depletion at the transcript level significantly impaired cell proliferation and apoptosis resistance in HCC cell lines. Notably, we discovered that the UBE2MP1 transcript shared a specific sequence, binding to the miR-145-5p seed region with a typical ceRNA effect. Simultaneously, we verified an axis of miR-145-5p/RGS3 in HCC cells, which promoted cell proliferation and apoptosis resistance with significance. And modulation of UE2MP1 could remarkably affect RGS3 expression and consequentially influence HCC cell growth in vitro. And combined with the rescue experiment modulating either miR-145-5p or RGS3 furtherly indicated UBE2MP1 as an upstream regulator of the axis in promoting HCC cell growth and maintenance. Thus, our findings provide new strategies for HCC prevention and individual treatment.