scholarly journals Identification and Classification of Reverse Transcriptases in Bacterial Genomes and Metagenomes

2021 ◽  
Author(s):  
Fatemeh Sharifi ◽  
Yuzhen Ye
Keyword(s):  
Template Switching ◽  
Group Ii Introns ◽  
Bacterial Genomes ◽  
Computational Tools ◽  
Reverse Transcriptases ◽  
Group Ii ◽  
Cell Suicide ◽  
Reference Genomes ◽  
Genomic Neighborhood

ABSTRACTReverse Transcriptases (RTs) are found in different systems including group II introns, Diversity Generating Retroelements (DGRs), retrons, CRISPR-Cas systems, and Abortive Infection (Abi) systems in prokaryotes. Different classes of RTs can play different roles, such as template switching and mobility in group II introns, spacer acquisition in CRISPR-Cas systems, mutagenic retrohoming in DGRs, programmed cell suicide in Abi systems, and recently discovered phage defense in retrons. While some classes of RTs have been studied extensively, others remain to be characterized. There is a lack of computational tools for identifying and characterizing various classes of RTs. In this study, we built a tool (called myRT) for identification and classification of prokaryotic RTs. In addition, our tool provides information about the genomic neighborhood of each RT, providing potential functional clues. We applied our tool to predict and classify RTs in all complete and draft bacterial genomes, and created a collection that can be used for exploration of putative RTs. Application of myRT to gut metagenomes showed that gut metagenomes encode proportionally more RTs related to DGRs, outnumbering retron-related RTs, as compared to the collection of reference genomes. MyRT is both available as a standalone software and also through a website.

scholarly journals Template switching by a group II intron reverse transcriptase: biochemical analysis and implications for RNA-seq

2019 ◽  
Author(s):  
Alfred M. Lentzsch ◽  
Jun Yao ◽  
Rick Russell ◽  
Alan M. Lambowitz
Keyword(s):  
Nucleic Acids ◽  
Group Ii Intron ◽  
Template Switching ◽  
Reverse Transcriptases ◽  
Donor And Acceptor ◽  
Nucleotide Addition ◽  
Single Base Pair ◽  
Group Ii ◽  
Template Switch ◽  
Template Dna

ABSTRACTThe reverse transcriptases (RTs) encoded by mobile group II intron and other non-LTR-retro-elements differ from retroviral RTs in being able to template switch from the 5’ end of one template to the 3’ end of another without pre-existing complementarity between the donor and acceptor nucleic acids. Here, we used the ability of a thermostable group II intron RT (TGIRT; GsI-IIC RT) to template switch directly from synthetic RNA template/DNA primer duplexes having either a blunt end or a 3’-DNA overhang end to establish a complete kinetic framework for the reaction and identify conditions that more efficiently capture acceptor RNAs or DNAs. The rate and amplitude of template switching are optimal from starter duplexes with a single nucleotide 3’-DNA overhang complementary to the 3’ nucleotide of the acceptor RNA, suggesting a role for non-templated nucleotide addition of a complementary nucleotide to the 3’ end of cDNAs synthesized from natural templates. Longer 3’-DNA overhangs progressively decrease the rate of template switching, even when complementary to the 3’ end of the acceptor template. The reliance on a single base pair with the 3’ nucleotide of the acceptor together with discrimination against mismatches and the high processivity of the enzyme enable synthesis of full-length DNA copies of nucleic acids beginning directly at their 3’ end. We discuss possible biological functions of the template-switching activity of group II intron and other non-LTR-retroelements RTs, as well as the optimization of this activity for adapter addition in RNA-and DNA-seq.

scholarly journals The Association of Group IIB Intron with Integrons in Hypersaline Environments

2020 ◽  
Author(s):  
Sarah Sonbol ◽  
Rania Siam
Keyword(s):  
Insertion Sequence ◽  
Soda Lake ◽  
Group Ii Introns ◽  
Extreme Halophile ◽  
Hypersaline Environments ◽  
Reverse Transcriptases ◽  
Blast Search ◽  
Efficient Gene ◽  
Group Ii

Abstract Background: Group II introns are mobile genetic elements used as efficient gene targeting tools. They function as both ribozymes and retroelements. Group IIC introns are the only class reported so far to be associated with integrons. In order to identify group II introns linked with integrons and CALINS (cluster of attC sites lacking a neighboring integron integrase) within halophiles, we mined for integrons in 28 assembled metagenomes from hypersaline environments and publically available 104 halophilic genomes using Integron Finder followed by blast search for group II intron reverse transcriptases (RT)s. Results: We report the presence of different group II introns associated with integrons and integron-related sequences denoted by UHB.I1, UHB.I2, H.ha.1 and H.ha.F2. The first two were identified within putative integrons in the metagenome of Tanatar-5 hypersaline soda lake, belonging to IIC and IIB intron classes, respectively. Truncated introns H.ha.F1 and H.ha.F2 were also detected in a CALIN within the extreme halophile Halorhodospira halochloris, both belonging to group IIB introns. The intron-encoded proteins (IEP)s identified within group IIB introns belonged to different classes: CL1 class in UHB.I2 and bacterial class E in H.ha.Fa1 and H.ha.F2. A newly identified insertion sequence (ISHahl1) of IS200/605 superfamily was also identified adjacent to H. halochloris CALIN. Finally, an abundance of toxin-antitoxin (TA) systems was observed within the identified integrons. Conclusion: So far, this is the first investigation of group II introns within integrons in halophilic genomes and metagenomes from hypersaline environments. We report the presence of group IIB introns associated with integrons or CALINs. This study provides the basis for understanding the role of group IIB introns in the evolution of halophiles and their potential biotechnological role.

scholarly journals The association of group IIB intron with integrons in hypersaline environments

Mobile DNA ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sarah Sonbol ◽  
Rania Siam
Keyword(s):  
Insertion Sequence ◽  
Soda Lake ◽  
Group Ii Introns ◽  
Extreme Halophile ◽  
Hypersaline Environments ◽  
Reverse Transcriptases ◽  
Blast Search ◽  
Efficient Gene ◽  
Group Ii

Abstract Background Group II introns are mobile genetic elements used as efficient gene targeting tools. They function as both ribozymes and retroelements. Group IIC introns are the only class reported so far to be associated with integrons. In order to identify group II introns linked with integrons and CALINS (cluster of attC sites lacking a neighboring integron integrase) within halophiles, we mined for integrons in 28 assembled metagenomes from hypersaline environments and publically available 104 halophilic genomes using Integron Finder followed by blast search for group II intron reverse transcriptases (RT)s. Results We report the presence of different group II introns associated with integrons and integron-related sequences denoted by UHB.F1, UHB.I2, H.ha.F1 and H.ha.F2. The first two were identified within putative integrons in the metagenome of Tanatar-5 hypersaline soda lake, belonging to IIC and IIB intron classes, respectively at which the first was a truncated intron. Other truncated introns H.ha.F1 and H.ha.F2 were also detected in a CALIN within the extreme halophile Halorhodospira halochloris, both belonging to group IIB introns. The intron-encoded proteins (IEP) s identified within group IIB introns belonged to different classes: CL1 class in UHB.I2 and bacterial class E in H.ha.Fa1 and H.ha.F2. A newly identified insertion sequence (ISHahl1) of IS200/605 superfamily was also identified adjacent to H. halochloris CALIN. Finally, an abundance of toxin-antitoxin (TA) systems was observed within the identified integrons. Conclusion So far, this is the first investigation of group II introns within integrons in halophilic genomes and metagenomes from hypersaline environments. We report the presence of group IIB introns associated with integrons or CALINs. This study provides the basis for understanding the role of group IIB introns in the evolution of halophiles and their potential biotechnological role.

scholarly journals Organellar Introns in Fungi, Algae, and Plants

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 2001
Author(s):  
Jigeesha Mukhopadhyay ◽  
Georg Hausner
Keyword(s):  
Gene Expression ◽  
Ribosomal Proteins ◽  
Heterologous Gene Expression ◽  
Group I Introns ◽  
Group Ii Introns ◽  
Homing Endonucleases ◽  
Organellar Genomes ◽  
Chloroplast Genomes ◽  
Group I ◽  
Group Ii

Introns are ubiquitous in eukaryotic genomes and have long been considered as ‘junk RNA’ but the huge energy expenditure in their transcription, removal, and degradation indicate that they may have functional significance and can offer evolutionary advantages. In fungi, plants and algae introns make a significant contribution to the size of the organellar genomes. Organellar introns are classified as catalytic self-splicing introns that can be categorized as either Group I or Group II introns. There are some biases, with Group I introns being more frequently encountered in fungal mitochondrial genomes, whereas among plants Group II introns dominate within the mitochondrial and chloroplast genomes. Organellar introns can encode a variety of proteins, such as maturases, homing endonucleases, reverse transcriptases, and, in some cases, ribosomal proteins, along with other novel open reading frames. Although organellar introns are viewed to be ribozymes, they do interact with various intron- or nuclear genome-encoded protein factors that assist in the intron RNA to fold into competent splicing structures, or facilitate the turn-over of intron RNAs to prevent reverse splicing. Organellar introns are also known to be involved in non-canonical splicing, such as backsplicing and trans-splicing which can result in novel splicing products or, in some instances, compensate for the fragmentation of genes by recombination events. In organellar genomes, Group I and II introns may exist in nested intronic arrangements, such as introns within introns, referred to as twintrons, where splicing of the external intron may be dependent on splicing of the internal intron. These nested or complex introns, with two or three-component intron modules, are being explored as platforms for alternative splicing and their possible function as molecular switches for modulating gene expression which could be potentially applied towards heterologous gene expression. This review explores recent findings on organellar Group I and II introns, focusing on splicing and mobility mechanisms aided by associated intron/nuclear encoded proteins and their potential roles in organellar gene expression and cross talk between nuclear and organellar genomes. Potential application for these types of elements in biotechnology are also discussed.

Self‐Splicing Group II Introns

Ribozymes ◽  
2021 ◽  
pp. 143-167
Author(s):  
Isabel Chillón ◽  
Marco Marcia
Keyword(s):  
Group Ii Introns ◽  
Group Ii ◽  
Self Splicing

scholarly journals Generalized bacterial genome editing using mobile group II introns and Cre‐ lox

2013 ◽  
Vol 9 (1) ◽  
pp. 685 ◽  
Author(s):  
Peter J Enyeart ◽  
Steven M Chirieleison ◽  
Mai N Dao ◽  
Jiri Perutka ◽  
Erik M Quandt ◽  
...  
Keyword(s):  
Genome Editing ◽  
Bacterial Genome ◽  
Group Ii Introns ◽  
Group Ii
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