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Sundarrajan S, Rao S, Padmanabhan S. Cloning and high-level expression of Thermus thermophilus RecA in E. coli: purification and novel use in HBV diagnostics. Braz J Microbiol 2018; 49:848-855. [PMID: 29691193 PMCID: PMC6175717 DOI: 10.1016/j.bjm.2018.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 03/08/2018] [Accepted: 03/13/2018] [Indexed: 11/25/2022] Open
Abstract
We studied the role of Thermus thermophilus Recombinase A (RecA) in enhancing the PCR signals of DNA viruses such as Hepatitis B virus (HBV). The RecA gene of a thermophilic eubacterial strain, T. thermophilus, was cloned and hyperexpressed in Escherichia coli. The recombinant RecA protein was purified using a single heat treatment step without the use of any chromatography steps, and the purified protein (>95%) was found to be active. The purified RecA could enhance the polymerase chain reaction (PCR) signals of HBV and improve the detection limit of the HBV diagnosis by real time PCR. The yield of recombinant RecA was ∼35mg/L, the highest yield reported for a recombinant RecA to date. RecA can be successfully employed to enhance detection sensitivity for the diagnosis of DNA viruses such as HBV, and this methodology could be particularly useful for clinical samples with HBV viral loads of less than 10IU/mL, which is interesting and novel.
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Affiliation(s)
- Sudarson Sundarrajan
- Cancyte Technologies Pvt. Ltd., Rangadore Memorial Hospital, Sri Shankara Research Center, Shankarapuram, Bangalore, India
| | - Sneha Rao
- Cancyte Technologies Pvt. Ltd., Rangadore Memorial Hospital, Sri Shankara Research Center, Shankarapuram, Bangalore, India
| | - Sriram Padmanabhan
- Cancyte Technologies Pvt. Ltd., Rangadore Memorial Hospital, Sri Shankara Research Center, Shankarapuram, Bangalore, India.
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Huang JF, Zhao N, Xu HQ, Xia H, Wei K, Fu WL, Huang Q. Sensitive and specific detection of miRNA using an isothermal exponential amplification method using fluorescence-labeled LNA/DNA chimera primers. Anal Bioanal Chem 2016; 408:7437-46. [PMID: 27485624 DOI: 10.1007/s00216-016-9829-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 07/17/2016] [Accepted: 07/25/2016] [Indexed: 10/21/2022]
Abstract
MicroRNAs (miRNAs) are currently considered as potential biomarkers for various human diseases. In the present study, miRNA-triggered real-time fluorescent isothermal reaction with exponential amplification (ReFIRE) with or without Thermus aquaticus MutS (Taq MutS) was developed to analyze miRNAs using DNA polymerase, a nicking endonuclease, and fluorescently labeled primers. In the absence of Taq MutS, the ReFIRE system permitted the detection of 100 ymol of targeted miRNA in 80 min. However, this system enabled limited differentiation between homologous miRNA family members. Upon addition of Taq MutS to the ReFIRE system, non-specific amplification generated from the mishybridization between primers and primer dimers or primers and the template duplex was eliminated. The addition of Taq MutS enabled the ultrasensitive detection of as little as 10 ymol of targeted miRNAs in 50 min, which corresponds to less than 10 copies of miRNAs in a total volume of 20 μl. Additionally, the assay exhibited a dynamic range of up to 12 orders of magnitude. The ReFIRE system also showed high specificity, enabling differentiation between homologous miRNA family members exhibiting only single-base differences. The sensitivity, specificity, and dynamic range associated with this system were greater than most currently available miRNA isothermal amplification assays. Moreover, when target-specific primers were labeled with different fluorescent reporters, multiplex analysis was easily performed in a single tube, permitting accurate normalization of miRNA expression. This simple, fast, ultrasensitive, highly specific, and easy-to-multiplex method could significantly contribute to research investigations pertaining to the biological roles of miRNA, as well as clinical diagnosis of various diseases that involve miRNA disruptions. Graphical Abstract The principle of ReFIRE system.
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Affiliation(s)
- Jun-Fu Huang
- Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Gaotanyan Road, Shapingba District, Chongqing, 400038, China
| | - Na Zhao
- Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Gaotanyan Road, Shapingba District, Chongqing, 400038, China
| | - Han-Qing Xu
- Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Gaotanyan Road, Shapingba District, Chongqing, 400038, China
| | - Han Xia
- Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Gaotanyan Road, Shapingba District, Chongqing, 400038, China
| | - Kun Wei
- Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Gaotanyan Road, Shapingba District, Chongqing, 400038, China
| | - Wei-Ling Fu
- Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Gaotanyan Road, Shapingba District, Chongqing, 400038, China.
| | - Qing Huang
- Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Gaotanyan Road, Shapingba District, Chongqing, 400038, China.
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