Flow Of Genetic Information Research Articles

A plant mutant screen CURE integrated with core biology concepts showed effectiveness in course design and students' perceived learning gains.

Course-based undergraduate research experiences (CUREs) provide students with valuable opportunities to engage in research in a classroom setting, expanding access to research opportunitiesfor undergraduates, fostering inclusive research and learning environments, and bridging the gap between the research and education communities. While scientific practices, integral to the scientific discovery process, have been widely implemented in CUREs, there have been relatively few reports emphasizing the incorporation of core biology concepts into CURE curricula. In this study, we present a CURE that integrates core biology concepts, including genetic information flow, phenotype-genotype relationships, mutations and mutants, and structure-function relationships, within the context of mutant screening and gene loci identification. The design of this laboratory course aligns with key CURE criteria, as demonstrated by data collected through the laboratory course assessment survey (LCAS). The survey of undergraduate research experiences (SURE) demonstrates students' learning gains in both course-directed skills and transferrable skills following their participation in the CURE. Additionally, concept survey data reflect students' self-perceived understanding of the aforementioned core biological concepts. Given that genetic mutant screens are central to the study of gene function in biology, we anticipate that this CURE holds potential value for educators and researchers who are interested in designing and implementing a mutant screen CURE in their classrooms. This can be accomplished through independent research or by establishing partnerships between different units or institutions.

PSLBII-27 Investigating the emergence of antimicrobial resistance in Mycoplasma bovis from feedlot cattle

Abstract Bovine respiratory disease (BRD) is the most significant disease affecting feedlot cattle in North America. Mycoplasma bovis is among the main BRD pathogenic bacteria. Infection control of M. bovis is hampered by a lack of effective vaccines and increasing antimicrobial resistance (AMR). Integrative and conjugative elements (ICEs) have been documented as a mechanism of horizontal gene transfer (HGT) in mycoplasmas. Mycoplasma ICEs (MICE) do not carry AMR genes but have been associated with the HGT of genes that confer AMR through point mutations. Hence, there is a need to gain a better understanding of the role of MICE in M. bovis AMR. Randomly selected M. bovis isolates (n = 54) collected from Western Canadian feedlot cattle (AB and SK) underwent whole-genome sequencing by short-reads (Illumina), with a subset (n = 6) selected based on AMR and ICE profiles for Oxford Nanopore long-read sequencing. Sequences were screened for the presence of MICE. MICE circularization (cMICE) is the first step of conjugation, and an in-house collection of 472 M. bovis field isolates (feedlot cattle just from AB) was screened by PCR for the presence of cMICE as a proxy for conjugation capabilities. Environmental conditions that could impact cMICE quantity, including growth phase, temperature, cell density, pH, starvation, UV light, CO2 concentration, and sub-inhibitory concentrations of mitomycin C were investigated by qPCR, followed by growth of M. bovis isolates under the most favorable conditions identified for cMICE-detection and screening by a high throughput qPCR method that eliminated the need for DNA extraction. Nineteen different mating pairs were carried out and 4 different environmental factors were tested for their possible impact on conjugation occurrence (incubation time, incubation volume, conjugation parent proportions, atmosphere). All isolates carried MICEs with 23/54 having a structure/sequence comparable to previously described functional MICE in mycoplasma, 43/54 possessing non-functional ICE, and 23 having >1 ICE. The presence of more than one MICE/genome suggests a lack of MICE (entry) exclusion systems in M. bovis, a trait that may promote the flow of genetic information among M. bovis isolates including AMR. Even though some factors including growth phase (early stationary phase) and pH (9.0) generated greater levels (≥1.5 fold) of cMICE, none of the examined parameters were statistically significant. However, as early stationary growth phase generated the greatest cMICE quantity (2.3 fold), M. bovis isolates were cMICE-screened at this growth stage for the expeditious identification of M. bovis conjugation candidates. A total of 25.7% M. bovis were cMICE-positive. Of 19 mating pairs tested, transconjugants were recovered from only 2 different mating pairs, possibly reflective of the need for further optimization of conjugation conditions.

Striving for clarity in language about gene expression.

What do we mean when we say 'gene expression'? In the decades following Crick's 1958 central dogma of molecular biology, whereby genetic information flows from DNA (genes) to RNA (transcripts) to protein (products), we have learned a great deal about DNA, RNA, proteins, and the ensuing phenotypic changes. With the advent of high-throughput technologies (1990s), molecular biologists and computer scientists forged critical collaborations to understand the vast amount of data being generated, rapidly escalating gene expression research to the 'omics' level: entire sets of genes (genomes), transcribed RNAs (transcriptomes), and synthesized proteins (proteomes). However, some concessions came to be made for molecular biologists and computer scientists to understand each other-one of the most prevalent being the increasingly widespread use of 'gene' to mean 'RNAs originating from a DNA segment'. This loosening of terminology, we will argue, creates ambiguity and confusion. We propose guidelines to increase precision and clarity when communicating about gene expression, most notably to reserve 'gene' for the DNA template and 'transcript' for the RNA transcribed from that gene. Striving to use perspicuous terminology will promote rigorous gene expression science and accelerate discovery in this highly promising area of biology.

Maximal Genetic Code Symmetry Is a Physicochemical Purine-Pyrimidine Symmetry Language for Transcription and Translation in the Flow of Genetic Information from DNA to Proteins.

Until now, research has not taken into consideration the physicochemical purine-pyrimidine symmetries of the genetic code in the transcription and translation processes of proteinogenesis. Our Supersymmetry Genetic Code table, developed in 2022, is common and unique for all RNA and DNA living species. Its basic structure is a purine-pyrimidine symmetry net with double mirror symmetry. Accordingly, the symmetry of the genetic code directly shows its organisation based on the principle of nucleotide Watson-Crick and codon-anticodon pairing. The maximal purine-pyrimidine symmetries of codons show that each codon has a strictly defined and unchangeable position within the genetic code. We discovered that the physicochemical symmetries of the genetic code play a fundamental role in recognising and differentiating codons from mRNA and the anticodon tRNA and aminoacyl-tRNA synthetases in the transcription and translation processes. These symmetries also support the wobble hypothesis with non-Watson-Crick pairing interactions between the translation process from mRNA to tRNA. The Supersymmetry Genetic Code table shows a specific arrangement of the second base of codons, according to which it is possible that an anticodon from tRNA recognises whether a codon from mRNA belongs to an amino acid with two or four codons, which is very important in the purposeful use of the wobble pairing process. Therefore, we show that canonical and wobble pairings essentially do not lead to misreading and errors during translation, and we point out the role of physicochemical purine-pyrimidine symmetries in decreasing disorder according to error minimisation and preserving the integrity of biological processes during proteinogenesis.

A spatial atlas of mitochondrial gene expression reveals dynamic translation hubs and remodeling in stress.

Mitochondrial genome expression is important for cellular bioenergetics. How mitochondrial RNA processing and translation are spatially organized across dynamic mitochondrial networks is not well understood. Here, we report that processed mitochondrial RNAs are consolidated with mitoribosome components into translation hubs distal to either nucleoids or processing granules in human cells. During stress, these hubs are remodeled into translationally repressed mesoscale bodies containing messenger, ribosomal, and double-stranded RNA. We show that the highly conserved helicase SUV3 contributes to the distribution of processed RNA within mitochondrial networks, and that stress bodies form downstream of proteostatic stress in cells lacking SUV3 unwinding activity. We propose that the spatial organization of nascent chain synthesis into discrete domains serves to throttle the flow of genetic information in stress to ensure mitochondrial quality control.

Synthetic genomes unveil the effects of synonymous recoding.

Engineering the genetic code of an organism provides the basis for (i) making any organism safely resistant to natural viruses and (ii) preventing genetic information flow into and out of genetically modified organisms while (iii) allowing the biosynthesis of genetically encoded unnatural polymers1-4. Achieving these three goals requires the reassignment of multiple of the 64 codons nature uses to encode proteins. However, synonymous codon replacement-recoding-is frequently lethal, and how recoding impacts fitness remains poorly explored. Here, we explore these effects using whole-genome synthesis, multiplexed directed evolution, and genome-transcriptome-translatome-proteome co-profiling on multiple recoded genomes. Using this information, we assemble a synthetic Escherichia coli genome in seven sections using only 57 codons to encode proteins. By discovering the rules responsible for the lethality of synonymous recoding and developing a data-driven multi-omics-based genome construction workflow that troubleshoots synthetic genomes, we overcome the lethal effects of 62,007 synonymous codon swaps and 11,108 additional genomic edits. We show that synonymous recoding induces transcriptional noise including new antisense RNAs, leading to drastic transcriptome and proteome perturbation. As the elimination of select codons from an organism's genetic code results in the widespread appearance of cryptic promoters, we show that synonymous codon choice may naturally evolve to minimize transcriptional noise. Our work provides the first genome-scale description of how synonymous codon changes influence organismal fitness and paves the way for the construction of functional genomes that provide genetic firewalls from natural ecosystems and safely produce biopolymers, drugs, and enzymes with an expanded chemistry.

The Leishmania ribosome: more than passive mRNA translating machinery

While the central dogma of molecular biology describes how genetic information flows, gene expression is also affected by epigenetic and epitranscriptomic processes. A recent report by Rajan et al. demonstrates how pseudouridylation of a Leishmania ribosomal rRNA affects the expression of particular proteins: an example of epitranslatomic control.

Recent Advances on Bioactive Molecules Acting on RNA and RNA Binding Proteins

This review discusses the binding of biologically active molecules to RNA, a crucial component in understanding the molecular basis of life. RNA is replicated from DNA by RNA polymerase and is essential for protein formation. Three types of cellular RNA are messenger RNA (mRNA), ribosomal RNA (rRNA), and soluble RNA (sRNA). The impact of altered RNA binding proteins on human diseases is also discussed. The article also discusses the function of human Pol III in transcription of noncoding RNAs with immuno stimulatory effects, which can promote antiviral immunity. The intricacies of RNA and RNA binding proteins (RBPs) have captivated researchers across various disciplines, owing to their pivotal roles in fundamental cellular processes and their emerging significance in disease mechanisms and therapeutics. RNA molecules, once considered mere messengers in the flow of genetic information, are now recognized as versatile regulators of gene expression, participating in transcriptional and translational control, RNA processing, and epigenetic modifications. In cancer cells, off-target signalling can be harmful, and a new mouse monoclonal antibody (6E4) targets 8-oxoA. RepRNA platforms have been found to lower bacterial lung burden and induce a spectrum of humoral and cellular immune responses. RNA-protein interactions can be inhibited and are potential therapeutic targets for various diseases. RNA-protein interactions can be inhibited and have both protective and pathogenic roles in some diseases. This review aims to provide a comprehensive overview of the recent advances in bioactive molecules binding on RNA and RBPs, encompassing key findings, technological breakthroughs, and therapeutic implications. By synthesizing current knowledge and identifying future directions, this review seeks to elucidate the multifaceted landscape of RNA biology and its implications for drug discovery and precision medicine.

Proxiome assembly of the plant nuclear pore reveals an essential hub for gene expression regulation.

The nuclear pore complex (NPC) is vital for nucleocytoplasmic communication. Recent evidence emphasizes its extensive association with proteins of diverse functions, suggesting roles beyond cargo transport. Yet, our understanding of NPC's composition and functionality at this extended level remains limited. Here, through proximity-labelling proteomics, we uncover both local and global NPC-associated proteome in Arabidopsis, comprising over 500 unique proteins, predominantly associated with NPC's peripheral extension structures. Compositional analysis of these proteins revealed that the NPC concentrates chromatin remodellers, transcriptional regulators and mRNA processing machineries in the nucleoplasmic region while recruiting translation regulatory machinery on the cytoplasmic side, achieving a remarkable orchestration of the genetic information flow by coupling RNA transcription, maturation, transport and translation regulation. Further biochemical and structural modelling analyses reveal that extensive interactions with nucleoporins, along with phase separation mediated by substantial intrinsically disordered proteins, may drive the formation of the unexpectedly large nuclear pore proteome assembly.

Fitness difference between two synonymous mutations of Phytophthora infestansATP6 gene

BackgroundSequence variation produced by mutation provides the ultimate source of natural selection for species adaptation. Unlike nonsynonymous mutation, synonymous mutations are generally considered to be selectively neutral but accumulating evidence suggests they also contribute to species adaptation by regulating the flow of genetic information and the development of functional traits. In this study, we analysed sequence characteristics of ATP6, a housekeeping gene from 139 Phytophthora infestans isolates, and compared the fitness components including metabolic rate, temperature sensitivity, aggressiveness, and fungicide tolerance among synonymous mutations.ResultsWe found that the housekeeping gene exhibited low genetic variation and was represented by two major synonymous mutants at similar frequency (0.496 and 0.468, respectively). The two synonymous mutants were generated by a single nucleotide substitution but differed significantly in fitness as well as temperature-mediated spatial distribution and expression. The synonymous mutant ending in AT was more common in cold regions and was more expressed at lower experimental temperature than the synonymous mutant ending in GC and vice versa.ConclusionOur results are consistent with the argument that synonymous mutations can modulate the adaptive evolution of species including pathogens and have important implications for sustainable disease management, especially under climate change.

Constructing analogies: Developing critical thinking through a collaborative task.

Analogies are used to make abstract topics meaningful and more easily comprehensible to learners. Incorporating simple analogies into STEM classrooms is a fairly common practice, but the analogies are typically generated and explained by the instructor for the learners. We hypothesize that challenging learners to create complex, extended analogies themselves can promote integration of content knowledge and development of critical thinking skills, which are essential for deep learning, but are challenging to teach. In this qualitative study, college biology students (n = 30) were asked to construct a complex analogy about the flow of genetic information using a familiar item. One week later, participants constructed a second analogy about the same topic, but this time using a more challenging item. Twenty participants worked on the challenging analogy in pairs, while the other 10 worked alone. Analysis of the 50 interviews resulted in a novel-scoring scheme, which measured both content knowledge (understanding of biology terms) and critical thinking (alignment of relationships between elements of the analogy). Most participants improved slightly due to practice, but they improved dramatically when working with a partner. The biggest gains were seen in critical thinking, not content knowledge. Having students construct complex, sophisticated analogies in pairs is a high-impact practice that can help students develop their critical thinking skills, which are crucial in academic and professional settings. The discussion between partners likely requires students to justify their explanations and critique their partner's explanations, which are characteristics of critical thinking.

To be mobile or not: the variety of reverse transcriptases and their recruitment by host genomes

Reverse transcriptases (RT), or RNA-dependent DNA polymerases, are unorthodox enzymes that originally added a new angle to the conventional view of the unidirectional flow of genetic information in the cell from DNA to RNA to protein. First discovered in vertebrate retroviruses, RTs were since re-discovered in most eukaryotes, bacteria, and archaea, spanning essentially all domains of life. For retroviruses, RTs provide the ability to copy the RNA genome into DNA for subsequent incorporation into the host genome, which is essential for their replication and survival. In cellular organisms, most RT sequences originate from retrotransposons, the type of self-replicating genetic elements that rely on reverse transcription to copy and paste their sequences into new genomic locations. Some retroelements, however, can undergo domestication, eventually becoming a valuable addition to the overall repertoire of cellular enzymes. They can be beneficial yet accessory, like the diversity-generating elements, or even essential, like the telomerase reverse transcriptases. Nowadays, ever-increasing numbers of domesticated RT-carrying genetic elements are being discovered. It may be argued that domesticated RTs and reverse transcription in general is more widespread in cellular organisms than previously thought, and that many important cellular functions, such as chromosome end maintenance, may evolve from an originally selfish process of converting RNA into DNA.

Chargaff's second parity rule lies at the origin of additive genetic interactions in quantitative traits to make omnigenic selection possible.

Francis Crick's central dogma provides a residue-by-residue mechanistic explanation of the flow of genetic information in living systems. However, this principle may not be sufficient for explaining how random mutations cause continuous variation of quantitative highly polygenic complex traits. Chargaff's second parity rule (CSPR), also referred to as intrastrand DNA symmetry, defined as near-exact equalities G ≈ C and A ≈ T within a single DNA strand, is a statistical property of cellular genomes. The phenomenon of intrastrand DNA symmetry was discovered more than 50 years ago; at present, it remains unclear what its biological role is, what the mechanisms are that force cellular genomes to comply strictly with CSPR, and why genomes of certain noncellular organisms have broken intrastrand DNA symmetry. The present work is aimed at studying a possible link between intrastrand DNA symmetry and the origin of genetic interactions in quantitative traits. Computational analysis of single-nucleotide polymorphisms in human and mouse populations and of nucleotide composition biases at different codon positions in bacterial and human proteomes. The analysis of mutation spectra inferred from single-nucleotide polymorphisms observed in murine and human populations revealed near-exact equalities of numbers of reverse complementary mutations, indicating that random genetic variations obey CSPR. Furthermore, nucleotide compositions of coding sequences proved to be statistically interwoven via CSPR because pyrimidine bias at the 3rd codon position compensates purine bias at the 1st and 2nd positions. According to Fisher's infinitesimal model, we propose that accumulation of reverse complementary mutations results in a continuous phenotypic variation due to small additive effects of statistically interwoven genetic variations. Therefore, additive genetic interactions can be inferred as a statistical entanglement of nucleotide compositions of separate genetic loci. CSPR challenges the neutral theory of molecular evolution-because all random mutations participate in variation of a trait-and provides an alternative solution to Haldane's dilemma by making a gene function diffuse. We propose that CSPR is symmetry of Fisher's infinitesimal model and that genetic information can be transferred in an implicit contactless manner.

Chemoproteomic Profiling of 8-Oxoguanosine-Sensitive RNA-Protein Interactions.

Cellular nucleic acids are subject to assault by endogenous and exogenous agents that can perturb the flow of genetic information. Oxidative stress leads to the accumulation of 8-oxoguanine (8OG) in DNA and RNA. 8OG lesions on mRNA negatively impact translation, but their effect on global RNA-protein interactions is largely unknown. Here, we apply an RNA chemical proteomics approach to investigate the effect of 8OG on RNA-protein binding. We find proteins that bind preferentially to 8OG-modified RNA, including IGF2BP1-3 and hnRNPD, and proteins that are repelled by 8OG such as RBM4. We characterize these interactions using biochemical and biophysical assays to quantify the effect of 8OG on binding and show that a single 8OG abolishes the binding of RBM4 to its preferred CGG-containing substrate. Taken together, our work establishes the molecular consequences of 8OG on cellular RNA-protein binding and provides a framework for interrogating the role of RNA oxidation in biological systems.

How RNA impacts DNA repair

The central dogma of molecular biology posits that genetic information flows unidirectionally, from DNA, to RNA, and finally to protein. However, this directionality is broken in some cases, such as reverse transcription where RNA is converted to DNA by retroviruses and certain transposable elements. Our genomes have evolved and adapted to the presence of reverse transcription. Similarly, our genome is continuously maintained by several repair pathways to reverse damage due to various endogenous and exogenous sources. More recently, evidence has revealed that RNA, while in certain contexts may be detrimental for genome stability, is involved in promoting certain types of DNA repair. Depending on the pathway in question, the size of these DNA repair-associated RNAs range from one or a few ribonucleotides to long fragments of RNA. Moreover, RNA is highly modified, and RNA modifications have been revealed to be functionally associated with specific DNA repair pathways. In this review, we highlight aspects of this unexpected layer of genomic maintenance, demonstrating how RNA may influence DNA integrity.

Inferring gene regulatory networks using transcriptional profiles as dynamical attractors.

Genetic regulatory networks (GRNs) regulate the flow of genetic information from the genome to expressed messenger RNAs (mRNAs) and thus are critical to controlling the phenotypic characteristics of cells. Numerous methods exist for profiling mRNA transcript levels and identifying protein-DNA binding interactions at the genome-wide scale. These enable researchers to determine the structure and output of transcriptional regulatory networks, but uncovering the complete structure and regulatory logic of GRNs remains a challenge. The field of GRN inference aims to meet this challenge using computational modeling to derive the structure and logic of GRNs from experimental data and to encode this knowledge in Boolean networks, Bayesian networks, ordinary differential equation (ODE) models, or other modeling frameworks. However, most existing models do not incorporate dynamic transcriptional data since it has historically been less widely available in comparison to "static" transcriptional data. We report the development of an evolutionary algorithm-based ODE modeling approach (named EA) that integrates kinetic transcription data and the theory of attractor matching to infer GRN architecture and regulatory logic. Our method outperformed six leading GRN inference methods, none of which incorporate kinetic transcriptional data, in predicting regulatory connections among TFs when applied to a small-scale engineered synthetic GRN in Saccharomyces cerevisiae. Moreover, we demonstrate the potential of our method to predict unknown transcriptional profiles that would be produced upon genetic perturbation of the GRN governing a two-state cellular phenotypic switch in Candida albicans. We established an iterative refinement strategy to facilitate candidate selection for experimentation; the experimental results in turn provide validation or improvement for the model. In this way, our GRN inference approach can expedite the development of a sophisticated mathematical model that can accurately describe the structure and dynamics of the in vivo GRN.

A New Epigenetic Crosstalk: Chemical Modification Information Flow.

Central dogma is the most fundamental hypothesis in the field of molecular biology and explains the genetic information flow from DNA to protein. Beyond residue-by-residue transmission of sequential information, chemical modifications of DNA, RNA, and protein are also relayed in the course of gene expression. Here, this work presents recent evidence supporting bidirectional interplay between chromatin modifications and RNA modifications. Furthermore, several RNA modifications likely affect chemical modifications of proteins. The relay of chemical modifications occurs co-transcriptionally or co-translationally, ensuring crosstalk among chemical modifications at the DNA, RNA, and protein levels. Overall, this work proposes a hypothetical framework that represents transmission of chemical modification information among chromatin, RNA, and proteins.

Biogenesis, Mode of Action and the Interactions of Plant Non-Coding RNAs.

The central dogma of genetics, which outlines the flow of genetic information from DNA to RNA to protein, has long been the guiding principle in molecular biology. In fact, more than three-quarters of the RNAs produced by transcription of the plant genome are not translated into proteins, and these RNAs directly serve as non-coding RNAs in the regulation of plant life activities at the molecular level. The breakthroughs in high-throughput transcriptome sequencing technology and the establishment and improvement of non-coding RNA experiments have now led to the discovery and confirmation of the biogenesis, mechanisms, and synergistic effects of non-coding RNAs. These non-coding RNAs are now predicted to play important roles in the regulation of gene expression and responses to stress and evolution. In this review, we focus on the synthesis, and mechanisms of non-coding RNAs, and we discuss their impact on gene regulation in plants.

RNA alternative splicing impacts the risk for alcohol use disorder

Alcohol use disorder (AUD) is a complex genetic disorder characterized by problems arising from excessive alcohol consumption. Identifying functional genetic variations that contribute to risk for AUD is a major goal. Alternative splicing of RNA mediates the flow of genetic information from DNA to gene expression and expands proteome diversity. We asked whether alternative splicing could be a risk factor for AUD. Herein, we used a Mendelian randomization (MR)-based approach to identify skipped exons (the predominant splicing event in brain) that contribute to AUD risk. Genotypes and RNA-seq data from the CommonMind Consortium were used as the training dataset to develop predictive models linking individual genotypes to exon skipping in the prefrontal cortex. We applied these models to data from the Collaborative Studies on Genetics of Alcoholism to examine the association between the imputed cis-regulated splicing outcome and the AUD-related traits. We identified 27 exon skipping events that were predicted to affect AUD risk; six of these were replicated in the Australian Twin-family Study of Alcohol Use Disorder. Their host genes are DRC1, ELOVL7, LINC00665, NSUN4, SRRM2 and TBC1D5. The genes downstream of these splicing events are enriched in neuroimmune pathways. The MR-inferred impacts of the ELOVL7 skipped exon on AUD risk was further supported in four additional large-scale genome-wide association studies. Additionally, this exon contributed to changes of gray matter volumes in multiple brain regions, including the visual cortex known to be involved in AUD. In conclusion, this study provides strong evidence that RNA alternative splicing impacts the susceptibility to AUD and adds new information on AUD-relevant genes and pathways. Our framework is also applicable to other types of splicing events and to other complex genetic disorders.

Transcription-translation coupling: Recent advances and future perspectives.

The flow of genetic information from the chromosome to protein in all living organisms consists of two steps: (1) copying information coded in DNA into an mRNA intermediate via transcription by RNA polymerase, followed by (2) translation of this mRNA into a polypeptide by the ribosome. Unlike eukaryotes, where transcription and translation are separated by a nuclear envelope, in bacterial cells, these two processes occur within the same compartment. This means that a pioneering ribosome starts translation on nascent mRNA that is still being actively transcribed by RNA polymerase. This tethering via mRNA is referred to as 'coupling' of transcription and translation (CTT). CTT raises many questions regarding physical interactions and potential mutual regulation between these large (ribosome is ~2.5 MDa and RNA polymerase is 0.5 MDa) and powerful molecular machines. Accordingly, we will discuss some recently discovered structural and functional aspects of CTT.