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McKinley LN, Kern RG, Assmann SM, Bevilacqua PC. Flanking Sequence Cotranscriptionally Regulates Twister Ribozyme Activity. Biochemistry 2024; 63:53-68. [PMID: 38134329 DOI: 10.1021/acs.biochem.3c00506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2023]
Abstract
Small nucleolytic ribozymes are RNAs that cleave their own phosphodiester backbone. While proteinaceous enzymes are regulated by a variety of known mechanisms, methods of regulation for ribozymes remain unclear. Twister is one ribozyme class for which many structural and catalytic properties have been elucidated. However, few studies have analyzed the activity of twister ribozymes in the context of a native flanking sequence, even though ribozymes as transcribed in nature do not exist in isolation. Interactions between the ribozyme and its neighboring sequences can induce conformational changes that inhibit self-cleavage, providing a regulatory mechanism that could naturally determine ribozyme activity in vivo and in synthetic applications. To date, eight twister ribozymes have been identified within the staple crop rice (Oryza sativa). Herein, we select several twister ribozymes from rice and show that they are differentially regulated by their flanking sequence using published RNA-seq data sets, structure probing, and cotranscriptional cleavage assays. We found that the Osa 1-2 ribozyme does not interact with its flanking sequences. However, sequences flanking the Osa 1-3 and Osa 1-8 ribozymes form inactive conformations, referred to here as "ribozymogens", that attenuate ribozyme self-cleavage activity. For the Osa 1-3 ribozyme, we show that activity can be rescued upon addition of a complementary antisense oligonucleotide, suggesting ribozymogens can be controlled via external signals. In all, our data provide a plausible mechanism wherein flanking sequence differentially regulates ribozyme activity in vivo. More broadly, the ability to regulate ribozyme behavior locally has potential applications in control of gene expression and synthetic biology.
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Affiliation(s)
- Lauren N McKinley
- Depatment of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Reuben G Kern
- Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Sarah M Assmann
- Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Philip C Bevilacqua
- Depatment of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
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In-Plant Persistence and Systemic Transport of Nicotiana benthamiana Retrozyme RNA. Int J Mol Sci 2022; 23:ijms232213890. [PMID: 36430367 PMCID: PMC9695139 DOI: 10.3390/ijms232213890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 11/08/2022] [Accepted: 11/08/2022] [Indexed: 11/16/2022] Open
Abstract
Retrozymes are nonautonomous retrotransposons with hammerhead ribozymes in their long terminal repeats (LTRs). Retrozyme transcripts can be self-cleaved by the LTR ribozyme, circularized, and can undergo RNA-to-RNA replication. Here, we demonstrate that the Nicotiana benthamiana genome contains hundreds of retrozyme loci, of which nine represent full-length retrozymes. The LTR contains a promoter directing retrozyme transcription. Although retrozyme RNA is easily detected in plants, the LTR region is heavily methylated, pointing to its transcriptional silencing, which can be mediated by 24 nucleotide-long retrozyme-specific RNAs identified in N. benthamiana. A transcriptome analysis revealed that half of the retrozyme-specific RNAs in plant leaves have no exact matches to genomic retrozyme loci, containing up to 13% mismatches with the closest genomic sequences, and could arise as a result of many rounds of RNA-to-RNA replication leading to error accumulation. Using a cloned retrozyme copy, we show that retrozyme RNA is capable of replication and systemic transport in plants. The presented data suggest that retrozyme loci in the N. benthamiana genome are transcriptionally inactive, and that circular retrozyme RNA can persist in cells due to its RNA-to-RNA replication and be transported systemically, emphasizing functional and, possibly, evolutionary links of retrozymes to viroids-noncoding circular RNAs that infect plants.
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Kim WR, Park EG, Lee YJ, Bae WH, Lee DH, Kim HS. Integration of TE Induces Cancer Specific Alternative Splicing Events. Int J Mol Sci 2022; 23:ijms231810918. [PMID: 36142830 PMCID: PMC9502224 DOI: 10.3390/ijms231810918] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 09/13/2022] [Accepted: 09/13/2022] [Indexed: 11/16/2022] Open
Abstract
Alternative splicing of messenger RNA (mRNA) precursors contributes to genetic diversity by generating structurally and functionally distinct transcripts. In a disease state, alternative splicing promotes incidence and development of several cancer types through regulation of cancer-related biological processes. Transposable elements (TEs), having the genetic ability to jump to other regions of the genome, can bring about alternative splicing events in cancer. TEs can integrate into the genome, mostly in the intronic regions, and induce cancer-specific alternative splicing by adjusting various mechanisms, such as exonization, providing splicing donor/acceptor sites, alternative regulatory sequences or stop codons, and driving exon disruption or epigenetic regulation. Moreover, TEs can produce microRNAs (miRNAs) that control the proportion of transcripts by repressing translation or stimulating the degradation of transcripts at the post-transcriptional level. Notably, TE insertion creates a cancer-friendly environment by controlling the overall process of gene expression before and after transcription in cancer cells. This review emphasizes the correlative interaction between alternative splicing by TE integration and cancer-associated biological processes, suggesting a macroscopic mechanism controlling alternative splicing by TE insertion in cancer.
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Affiliation(s)
- Woo Ryung Kim
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Eun Gyung Park
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Yun Ju Lee
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Woo Hyeon Bae
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Du Hyeong Lee
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Heui-Soo Kim
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
- Department of Biological Sciences, College of Natural Sciences, Pusan National University, Busan 46241, Korea
- Correspondence:
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