Poly (A)-specific ribonuclease deficiency impacts oogenesis in zebrafish.

Poly (A)-specific ribonuclease (PARN) is the most important 3'-5'exonuclease involved in the process of deadenylation, the removal of poly (A) tails of mRNAs. Although PARN is primarily known for its role in mRNA stability, recent studies suggest several other functions of PARN including a role in telomere biology, non-coding RNA maturation, trimming of miRNAs, ribosome biogenesis and TP53 function. Moreover, PARN expression is de-regulated in many cancers, including solid tumours and hematopoietic malignancies. To better understand the in vivo role of PARN, we used a zebrafish model to study the physiological consequences of Parn loss-of-function. Exon 19 of the gene, which partially codes for the RNA binding domain of the protein, was targeted for CRISPR-Cas9-directed genome editing. Contrary to the expectations, no developmental defects were observed in the zebrafish with a parn nonsense mutation. Intriguingly, the parn null mutants were viable and fertile, but turned out to only develop into males. Histological analysis of the gonads in the mutants and their wild type siblings revealed a defective maturation of gonadal cells in the parn null mutants. The results of this study highlight yet another emerging function of Parn, i.e., its role in oogenesis.

Sequence-Specific Gene Silencing of acrA in the Multi-drug Efflux System AcrAB Induces Sensitivity in Drug-Resistant Klebsiella pneumoniae.

Multi-drug efflux is one of the resistant determinants in Klebsiella pneumoniae that are encountered in a broad range of clinically relevant antimicrobial agents. An alternative method to strategically induce sensitivity in drug-resistant K. pneumoniae and improve the efficacy of the existing antibiotics is the need of the hour. Hence, an antisense RNA was designed against the acrA gene of the AcrAB-TolC efflux system in a drug-resistant isolate of K. pneumoniae obtained from a blood culture. Minimum inhibitory concentration by E test demonstrated that the antisense RNA could significantly increase the susceptibility of previously resistant K. pneumoniae toward ciprofloxacin (CIP) and co-trimoxazole. Real-time PCR determined the ability of the antisense RNA to inhibit the expression of the acrA-mRNA. The wild-type K. pneumoniae showed increased growth in the presence of CIP, while, under the same condition, the growth of the antisense RNA-treated K. pneumoniae was inhibited up till 12 h. In the presence of co-trimoxazole, delayed growth rate of the antisense RNA-treated K. pneumoniae was seen, in comparison to that of the wild-type K. pneumoniae and also a fourfold reduction was noted in the expression of the efflux gene acrA. Our results underscore the potential of the acrA antisense RNA as an alternative therapeutic against multi-drug-resistant K. pneumoniae.

PARN Knockdown in Cell Lines Results in Differential and Cell-Specific Alterations in the Expression of Cancer-Associated mRNAs.

Ribonucleases (RNases) is the collective term used for the group of enzymes that are involved in mRNA degradation. The shortening of the poly (A) tail through deadenylation is the preferred mechanism of degradation of most eukaryotic mRNAs and poly (A)-specific ribonuclease (PARN) is the most important player in deadenylation.  Besides its primarily role in mRNA stability, PARN is also involved in several non-conventional functions. It is conceivable that a decreased RNase activity can alter the stability of cancer-associated mRNAs and this alteration may be differential in cells of different origin. METHODS: The effects of siRNA-mediated knockdown of PARN on the post-transcriptional expression of 16 oncogenes and 18 tumor suppressor genes in cells derived from different lineages (NCI-H460 and NCI-H522; lung cancer) and (HEK-293; kidney) were investigated. Further, the effects of PARN depletion on proliferation and death of the lung cancer cells were investigated. RESULTS: Quantitative real time PCR analysis revealed an cell-specific alteration in the expression of the target onco and tumor suppressor genes upon PARN depletion, differently, for cells derived from different lineages. The tumor suppressor genes showed a consistent pattern of down regulation upon PARN depletion in all the three cell types tested. In contrast, the expression of oncogenes was not consistent; while some oncogenes showed overexpression in HEK 293 cells, the majority of them were downregulated in the lung cancer cells. Further, PARN depletion did not alter the proliferation of lung cancer cells, which was in contrast to previous reports. CONCLUSION: The results of this study reveal that PARN deficiency leads to an altered stability of cancer-associated mRNA, distinctly, in cells of different lineages. Despite previous reports suggesting a potential therapeutic role of PARN in cancer, our results suggest that PARN may not be an important biomarker, particularly in lung cancer.

Poly (A)-specific ribonuclease (PARN): More than just "mRNA stock clearing".

In eukaryotic cells, the balance between the synthesis and the degradation decides the steady-state levels of messenger RNAs (mRNA). The removal of adenosine residues from the poly(A) tail, called deadenylation, is the first and the most crucial step in the process of mRNA degradation. Poly (A)-specific ribonuclease (PARN) is one such enzyme that catalyses the process of deadenylation. Although PARN has been primarily known as the regulator of the mRNA stability, recent evidence clearly suggests several other functions of PARN, including a role in embryogenesis, oocyte maturation, cell-cycle progression, telomere biology, non-coding RNA maturation and ribosome biogenesis. Also, deregulated PARN activity is shown to be a hallmark of specific disease conditions. Pathogenic variants in the PARN gene have been observed in various cancers and inherited bone marrow failure syndromes. The focus in this review is to highlight the emerging functions of PARN, particularly in the context of human diseases.

TP53 codon 72 polymorphism and type 2 diabetes: a case-control study in South Indian population.

TP53 functions primarily as a tumor suppressor, controlling a myriad of signalling pathways that prevent a cell from undergoing malignant transformation. This tumor suppressive function requires an activation and stabilization of TP53 in response to cell stressors. However, besides its cancer-preventive functions, TP53 is also known to be involved in diverse cellular processes including metabolism, reproduction, stem cell renewal and development. Indeed, several lines of evidence strongly suggest that TP53 plays crucial role in diabetes. A number of studies have evaluated the association of genetic alterations (single nucleotide variations) in TP53 gene with the development of diabetes. However, the results have not been consistent. The aim of this study was to evaluate whether the C/G polymorphism at codon 72 (Pro72/Arg72), located in exon 4 of TP53, is associated with type 2 diabetes in South Indian population. A total of 74 type 2 diabetic patients and 54 non-diabetic subjects were screened. None of the three genotypes, namely C/C (Pro/Pro), C/G (Pro/Arg), and G/G (Arg/Arg) was found to be significantly associated with type 2 diabetes in our study group. The findings of this study indicate that TP53 codon 72 polymorphism is not associated with increased risk of type 2 diabetes in South Indian population. Further studies with a large cohort size would be necessary to corroborate the observations of this study. Nevertheless, this study represents the first genetic analysis of TP53 variants in South Indian type 2 diabetic patients.

Non-invasive detection of EGFR mutations by cell-free loop-mediated isothermal amplification (CF-LAMP).

Targeting epidermal growth factor receptor (EGFR) through tyrosine kinase inhibitors (TKI) is a successful therapeutic strategy in non-small cell lung cancer. However, the response to TKI therapy depends on specific activating and acquired mutations in the tyrosine kinase domain of the EGFR gene. Therefore, confirming the EGFR status of patients is crucial, not only for determining the eligibility, but also for monitoring the emergence of mutations in patients under TKI therapy. In this study, our aim was to develop a cost effective, yet sensitive, technique that allows the detection of therapeutically-relevant EGFR hotspot mutations at isothermal conditions in a non-invasive manner. Previously, we developed an allele-specific loop-mediated isothermal amplification (AS-LAMP) assay for screening germline and somatic de novo T790M EGFR mutation in lung cancer patients. In this study, we used cell free DNA as a template in AS-LAMP assay (CF-LAMP) for non-invasive detection of two hotspot EGFR mutations (T790M, and L858R) and compared its efficiency with ultrasensitive droplet digital PCR (ddPCR) assay. The results of CF-LAMP assay were consistent with those obtained in ddPCR assay, indicating the robustness of the method. CF-LAMP may serve as a valuable and cost-effective alternative for liquid biopsy techniques used in molecular diagnosis of non-small cell lung cancer.