PKR activation by a non-coding RNA expressed in lymphocytes of mice bearing B16 melanoma

Intratumoral injection of PKR shRNA expressing plasmid inhibits B16-F10 melanoma growth

The RNA-dependent protein kinase (PKR) is a serine/threonine kinase that is involved in the regulation of important cell processes such as apoptosis, signal transduction, cell proliferation and differentiation. However, the role played by PKR in cancer remains controversial. RNA interference (RNAi) has currently become an important technique in understanding gene function. Previously, we showed that PKR shRNA downregulates PKR expression in B16-F10 melanoma cells and reduces the metastatic potential of these tumor cells. In the present study, we examined the effect of the intratumoral injection of PKR shRNA‑expressing plasmid on the growth of B16-F10 melanoma in mice. The results showed that this treatment significantly reduced tumor growth. Thus, these findings suggested that PKR acts as a tumor suppressor, a finding that is consistent with our previous study on the experimental model of metastasis. Moreover, the results suggested that this effect may be mediated by the transcription factor NF-κB. The present study confirmed the hypothesis that the direct administration of RNAi-based therapeutics in the target tumor is a promising approach for overcoming the obstacles of systemic delivery. The results also suggested that the intratumoral injection of PKR shRNA‑expressing vector is a novel therapeutic approach for human solid tumors such as cutaneous melanoma and breast cancer, since PKR is overexpressed in these tumors.

Non-coding RNAs revealed during identification of genes involved in chicken immune responses

Recent large-scale cDNA cloning studies have shown that a significant proportion of the transcripts expressed from vertebrate genomes do not appear to encode protein. Moreover, it was reported in mammals (human and mice) that these non-coding transcripts are expressed and regulated by mechanisms similar to those involved in the control of protein-coding genes. We have produced a collection of cDNA sequences from immunologically active tissues with the aim of discovering chicken genes involved in immune mechanisms, and we decided to explore the non-coding component of these immune-related libraries. After finding known non-coding RNAs (miRNA, snRNA, snoRNA), we identified new putative mRNA-like non-coding RNAs. We characterised their expression profiles in immune-related samples. Some of them showed changes in expression following viral infections. As they exhibit patterns of expression that parallel the behaviour of protein-coding RNAs in immune tissues, our study suggests that they could play an active role in the immune response.

Non-protein coding RNA biomarkers and differential expression in cancers: a review

BACKGROUND

In these years a huge number of human transcripts has been found that do not code for proteins, named non-protein coding RNAs. In most cases, small (miRNAs, snoRNAs) and long RNAs (antisense RNA, dsRNA, and long RNA species) have many roles, functioning as regulators of other mRNAs, at transcriptional and post-transcriptional level, and controlling protein ubiquitination and degradation. Various species of npcRNAs have been found differentially expressed in different types of cancer. This review discusses the published data and new results on the expression of a subset of npcRNAs.

CONCLUSION

These results underscore the complexity of the RNA world and provide further evidence on the involvement of functional RNAs in cancer cell growth control.

Knockdown of PKR expression by RNAi reduces pulmonary metastatic potential of B16-F10 melanoma cells in mice: possible role of NF-kappaB

It was suggested that PKR may act as a tumor suppressor. However, the results are still controversial. Here, we investigate the effect of PKR-specific short hairpin RNA (shRNA) expressing plasmids on pulmonary metastatic potential of B16-F10 melanoma cells in mice. Levels of both PKR mRNA and PKR protein were only significantly reduced in tumor cells transfected with plasmid-based PKR-specific shRNA. Injection of tumor cells transfected with PKR-specific shRNA expressing plasmid resulted in inhibition (85%) of metastatic nodules compared with control. Our results suggest that this effect is mediated by the transcription factor NF-kappaB. This study does not support the concept of PKR as a tumor suppressor.

Non-coding transcript in T cells (NTT): antisense transcript activates PKR and NF-kappaB in human lymphocytes

T cell activation is a complex process involving many steps and the role played by the non-protein-coding RNAs (ncRNAs) in this phenomenon is still unclear. The non-coding T cells transcript (NTT) is differentially expressed during human T cells activation, but its function is unknown. Here, we detected a 426 nt NTT transcript by RT-PCR using RNA of human lymphocytes activated with a synthetic peptide of HIV-1. After cloning, the sense and antisense 426 nt NTT transcripts were obtained by in vitro transcription and were sequenced. We found that both transcripts are highly structured and are able to activate PKR. A striking observation was that the antisense 426 nt NTT transcript is significantly more effective in activating PKR than the corresponding sense transcript. The transcription factor NF-kappaB is activated by PKR through phosphorylation and subsequent degradation of its inhibitor I-kappaBbeta. We also found that the antisense 426 nt NTT transcript induces more efficiently the degradation of I-kappaBbeta than the sense transcript. Thus, this study suggests that the role played by NTT in the activation of lymphocytes can be mediated by PKR through NF-kappaB activation. However, the physiological significance of the activity of the antisense 426 nt NTT transcript remains unknown.

What is so special about oskar wild?

The amazing world of regulatory noncoding RNA has been at the center of biologists' attention in many different fields, from structural biology to transcriptional regulation and cell signaling. The latest example comes from developmental biology. A mutation in the Drosophila gene Oskar reveals a novel developmental function for the 3' untranslated region (UTR) of the oscar mRNA. This study further suggests that, when transcribed, the noncoding parts of the genome may well carry essential regulatory functions fundamental for the coordinated gene expression and development of multicellular organisms.