Consequences Of Regulation Research Articles

Financial crime: Why are securities markets vulnerable?

In the last five years, regulators have begun to focus on compliance and money laundering risks specific to securities markets. It is clear to them that the ways in which securities are issued, traded, cleared and settled create a series of opportunities for criminals and that these opportunities make the securities industry vulnerable to financial crime. This paper explains where the vulnerabilities lie in securities markets, explores the regulatory and financial consequences for individual firms of failing to address these vulnerabilities, identifies guides to action and obstacles to effective compliance and discusses how they can be overcome at affordable cost.

Smart-RRBS for single-cell methylome and transcriptome analysis.

The integration of DNA methylation and transcriptional state within single cells is of broad interest. Several single-cell dual- and multi-omics approaches have been reported that enable further investigation into cellular heterogeneity, including the discovery and in-depth study of rare cell populations. Such analyses will continue to provide important mechanistic insights into the regulatory consequences of epigenetic modifications. We recently reported a new method for profiling the DNA methylome and transcriptome from the same single cells in a cancer research study. Here, we present details of the protocol and provide guidance on its utility. Our Smart-RRBS (reduced representation bisulfite sequencing) protocol combines Smart-seq2 and RRBS and entails physically separating mRNA from the genomic DNA. It generates paired epigenetic promoter and RNA-expression measurements for ~24% of protein-coding genes in a typical single cell. It also works for micro-dissected tissue samples comprising hundreds of cells. The protocol, excluding flow sorting of cells and sequencing, takes ~3 d to process up to 192 samples manually. It requires basic molecular biology expertise and laboratory equipment, including a PCR workstation with UV sterilization, a DNA fluorometer and a microfluidic electrophoresis system.

The Ethical Digital Surgeon.

This viewpoint explores the ethical and regulatory consequences of the digital transformation of the operating room. Surgical robotics is undergoing significant change and future advances will center around the capture and use of data. The consequences of creating this surgical data pipeline must be understood and digital surgical systems must prioritize the safeguarding of patient data. Moreover, data protection laws and frameworks must adapt to the changing nature of surgical data. Finally, digital surgeons must understand changing data legislation and best practice on data governance to act as guardians not only for their own but also for their patients’ data.

The Implementation of Entrustable Professional Activities in Postgraduate Medical Education in the Netherlands: Rationale, Process, and Current Status.

Postgraduate medical education in the Netherlands has adopted competency-based education since the turn of the century. In 2006, the CanMEDS competency framework was introduced. A 2013 government plan to reduce the length and budgets of training programs led the Dutch Association of Medical Specialists (DAMS) to respond with a proposal to create more flexibility and individualization rather than a blunt cut in the length across all training programs. DAMS launched a government-funded, nation-wide, 4-year project (2014-2018) to blueprint the reform of postgraduate medical education in this direction. To achieve competency-based individualization, the fixed duration of postgraduate programs was abandoned, and entrustable professional activities (EPAs) were introduced in all specialty programs. Implementation of this new generation of programs took place in 2017-2019 in all disciplines. The project focused on EPA-based individualization of all programs, while addressing issues of the continuity of patient care in time-variable programs and the legal and regulatory consequences of individualization. About 30 specialty programs were revised at national, regional, local, and individual levels to incorporate EPAs; portfolio systems were adapted, clinical competency committees were installed for all programs, and procedures for summative entrustment decision making were elaborated. This paper reports on the rationale and the process that led to a more time-variable postgraduate education landscape, and, on average, a shortening of training length by 3 months.

Regulatory Perspectives of Pyrrolizidine Alkaloid Contamination in Herbal Medicinal Products.

The toxicity of plants containing certain pyrrolizidine alkaloids has long been recognized in grazing animals and humans. Genotoxicity and carcinogenicity data from in vitro and in vivo (animal) studies were published over the last few decades for some of the 1,2-unsaturated pyrrolizidine alkaloids, leading to regulatory action on herbal medicinal products with pyrrolizidine alkaloid-containing plants more than 30 years ago. In recent years, it has become evident that in addition to herbal medicinal products containing pyrrolizidine alkaloid-containing plants, these products may also contain pyrrolizidine alkaloids without actually including pyrrolizidine alkaloid-containing plants. This is explained by contamination by accessory herbs (weeds). The national competent authorities of the European member states and the European Medicines Agency, in this case, the Committee on Herbal Medicinal Products, reacted to these findings by setting limits for all herbal medicinal products. This review article will briefly discuss the data leading to the establishment of thresholds and the regulatory developments and consequences, as well as the current discussions and research in this area.

The cis-regulatory effects of modern human-specific variants.

The Neanderthal and Denisovan genomes enabled the discovery of sequences that differ between modern and archaic humans, the majority of which are noncoding. However, our understanding of the regulatory consequences of these differences remains limited, in part due to the decay of regulatory marks in ancient samples. Here, we used a massively parallel reporter assay in embryonic stem cells, neural progenitor cells, and bone osteoblasts to investigate the regulatory effects of the 14,042 single-nucleotide modern human-specific variants. Overall, 1791 (13%) of sequences containing these variants showed active regulatory activity, and 407 (23%) of these drove differential expression between human groups. Differentially active sequences were associated with divergent transcription factor binding motifs, and with genes enriched for vocal tract and brain anatomy and function. This work provides insight into the regulatory function of variants that emerged along the modern human lineage and the recent evolution of human gene expression.

Abstract PO012: Characterization of molecular, phenotypic, and drug sensitivity changes due to estrogen receptor alpha mutations in endometrial cancer

Abstract Estrogen signaling is essential for normal uterine function and has been shown to play critical roles in the development of endometrial cancer. Mutations in the ligand binding domain (LBD) of estrogen receptor alpha (ER) have been identified in primary endometrial cancer and hormone therapy resistant breast cancer. In endometrial cancer, ER mutations are associated with worse outcomes and obesity independent disease. However, additional molecular and phenotypic characterizations of these mutations are needed in the context of endometrial cancer. Utilizing a CRISPR/Cas9 tagging strategy to model the more common Y537S and D538G LBD mutations while epitope tagging ER’s endogenous locus in Ishikawa cells, we studied the regulatory and phenotypic consequences of mutant ER in endometrial cancer and have identified potential targeted therapies for the treatment of this disease. RNA sequencing (RNA-seq) experiments uncovered expression changes caused by ER mutations, including both estradiol-regulated genes and mutation-specific, estradiol-independent genes. We found mutation-specific changes in gene expression were not recapitulated with prolonged estrogen exposure in wildtype cells, suggesting the mutant ER transcriptome is distinct from constitutive ER activity. The unique mutant ER expression program was related to phenotypic changes in ER mutant endometrial cancer cells, including increased proliferation specifically in vivo and increased migration in vitro relative to wildtype cells, consistent with more aggressive endometrial tumors. Based on the transcriptional and phenotypic alterations caused by mutant ER, we explored gene regulation based drugs for the potential treatment of mutant ER endometrial tumors. We found that two small molecules, cyclin dependent kinase 9 (CDK9) inhibitor Alvocidib and steroid receptor coactivator 3 (SRC-3) inhibitor SI-2, decreased mutant ER’s ability to promote proliferation and migration. In conclusion, mutant ER confers estrogen-independent activity while causing additional regulatory changes in endometrial cancer cells. This activity has led us to identify two drugs that show efficacy in treating mutant ER endometrial cancer cells, however further study is needed to ascertain whether they can be utilized as novel therapeutic targets in this disease. Citation Format: Zannel Blanchard, Jeffery M. Vahrenkamp, Spencer Arnesen, Kristofer C. Berrett, Jason Gertz. Characterization of molecular, phenotypic, and drug sensitivity changes due to estrogen receptor alpha mutations in endometrial cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference: Endometrial Cancer: New Biology Driving Research and Treatment; 2020 Nov 9-10. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(3_Suppl):Abstract nr PO012.

Constructing consumers: regulatory and methodological consequences of defining consumer preferences in European health claim regulation

This paper presents an analysis of the underlying assumptions and choices of the European regulatory process for health claims. The latter are scientifically substantiated statements, usually in the form of food labels, regarding the health benefits that a food may confer upon its consumer. We show that the European regulator (the European Food Safety Authority, EFSA) has adopted a particular construction (or definition) of a ‘standard consumer’ of foods with health claims, as well as chosen to give preeminent importance to one particular objective of this regulation (protecting consumers from false claims). EFSA’s choices of standards of proof (establishment of causality between food intake and desired outcome) and scientific methodology (randomized controlled trials) are coherent with this objective and the adopted definition of the consumer. We argue that it is not clear if consumers will react to the regulation as intended by the regulator, due to the possibility that only a fraction of consumers actually correspond to the regulator’s definition of a standard consumer of foods with health claims. We conclude that only empirical research on actual consumer uptake of the EU regulation would allow for an assessment of its effectiveness.

Constitutional justice and civil society in search of dialogue

The Russian constitutional justice is going through a stage of deep reforming. Both the nature of the participation of the Constitutional Court of the Russian Federation in the constitutional reform of 2020, as well as the content itself and regulatory consequences have exposed a serious value and institutional crisis of the identity of the Constitutional Court of the Russian Federation in the State-legal system. The main vector of the reform declared in order to “strengthen the role of the Constitutional Court of the Russian Federation” is essentially resulted from the authoritarian, not humanistic paradigm, and leads to the development of the integration of constitutional justice into a unified system of public power remaining without proper legal deterrence. The noted crisis of the identity of the constitutional justice, which reflects the general problems of Russian constitutionalism, is to a large extent a product and expression of a fundamental communicative constitutional crisis, failures in establishing a constitutional dialogue between the government and civil society. At the same time, constitutional justice is not only the object of this communication with its defects and dysfunctions but should act as one of its main subjects, it has a unique extremely important potential for implementing the values and practices of constitutional dialogue with civil society, especially in the conditions of post-socialism. The constitutional dialogue also characterizes the content side of the constitutional justice itself in its modern understanding. In this context, the article discusses both general issues related to the understanding of constitutional dialogue itself and its importance for constitutional justice, as well as some more specific problems of implementing the dialogic model of constitutional-judicial control in Russian realities. Determining the direction of the further evolution of the constitutional justice, which has a unique potential for self-transformation, in any case, is an important area of responsibility of civil society, which itself must remain resolute in organizing the constitutional dialogue, not avoid attempts to initiate it and insist on it.

Challenging infant-directed singing as a credible signal of maternal attention.

I challenge Mehr et al.'s contention that ancestral mothers were reluctant to provide all the attention demanded by their infants. The societies in which music emerged likely involved foraging mothers who engaged in extensive infant carrying, feeding, and soothing. Accordingly, their singing was multimodal, its rhythms aligned with maternal movements, with arousal regulatory consequences for singers and listeners.

DNA methylation during human adipogenesis and the impact of fructose

BackgroundIncreased adipogenesis and altered adipocyte function contribute to the development of obesity and associated comorbidities. Fructose modified adipocyte metabolism compared to glucose, but the regulatory mechanisms and consequences for obesity are unknown. Genome-wide methylation and global transcriptomics in SGBS pre-adipocytes exposed to 0, 2.5, 5, and 10 mM fructose, added to a 5-mM glucose-containing medium, were analyzed at 0, 24, 48, 96, 192, and 384 h following the induction of adipogenesis.ResultsTime-dependent changes in DNA methylation compared to baseline (0 h) occurred during the final maturation of adipocytes, between 192 and 384 h. Larger percentages (0.1% at 192 h, 3.2% at 384 h) of differentially methylated regions (DMRs) were found in adipocytes differentiated in the glucose-containing control media compared to adipocytes differentiated in fructose-supplemented media (0.0006% for 10 mM, 0.001% for 5 mM, and 0.005% for 2.5 mM at 384 h). A total of 1437 DMRs were identified in 5237 differentially expressed genes at 384 h post-induction in glucose-containing (5 mM) control media. The majority of them inversely correlated with the gene expression, but 666 regions were positively correlated to the gene expression.ConclusionsOur studies demonstrate that DNA methylation regulates or marks the transformation of morphologically differentiating adipocytes (seen at 192 h), to the more mature and metabolically robust adipocytes (as seen at 384 h) in a genome-wide manner. Lower (2.5 mM) concentrations of fructose have the most robust effects on methylation compared to higher concentrations (5 and 10 mM), suggesting that fructose may be playing a signaling/regulatory role at lower concentrations of fructose and as a substrate at higher concentrations.

Mutational analysis of Escherichia coli GreA protein reveals new functional activity independent of antipause and lethal when overexpressed

There is a growing appreciation for the diverse regulatory consequences of the family of proteins that bind to the secondary channel of E. coli RNA polymerase (RNAP), such as GreA, GreB or DksA. Similar binding sites could suggest a competition between them. GreA is characterised to rescue stalled RNAP complexes due to its antipause activity, but also it is involved in transcription fidelity and proofreading. Here, overexpression of GreA is noted to be lethal independent of its antipause activity. A library of random GreA variants has been used to isolate lethality suppressors to assess important residues for GreA functionality and its interaction with the RNA polymerase. Some mutant defects are inferred to be associated with altered binding competition with DksA, while other variants seem to have antipause activity defects that cannot reverse a GreA-sensitive pause site in a fliC::lacZ reporter system. Surprisingly, apparent binding and cleavage defects are found scattered throughout both the coiled-coil and globular domains. Thus, the coiled-coil of GreA is not just a measuring stick ensuring placement of acidic residues precisely at the catalytic centre but also seems to have binding functions. These lethality suppressor mutants may provide valuable tools for future structural and functional studies.

Methodological basis of state regulation of civil society finances

Civil society organizations can play an important role in the process of solving the significant social and economic problems at both the local and national levels. However, their contribution depends significantly on the environment in which they are functioning and on the current state of organizing of their finances. The current state of organizing and functioning of civil society finances depends on the state regulation process in this sphere. It is important that the state regulatory activity is carried out on the certain methodology. This article is devoted to the study of the basics of it. The purpose of the paper is to reveal the methodological basis of state regulation of civil society finances. The paper provides a comprehensive study of the methodological basis of state regulation of civil society finances in accordance with the generalized scheme of methodology of any activity. The main characteristics of state activity in the field of civil society finance regulation (features of state regulatory activity in the field of civil society finance, its principles, conditions and norms), logical structure of state regulatory activity in civil society finance (subjects, object of state regulatory activity, its forms, methods, means, results and consequences), as well as its time structure (phases, stages, stages) are studied. On the basis of the carried out research the author's scheme of methodological bases of the state regulation of finances of the civil society is formed. Implementation of the state regulation of civil society finances in accordance with the elements of the proposed scheme is important, because it has a great impact on the results and consequences for the population, the state, business and business structures and for the civil society itself.

The Market as a Learning Algorithm: Consequences for Regulation and Antitrust

The heart of the Chicago School’s attack on the antitrust laws was a skepticism about the ability of government to improve upon unregulated market outcomes. Although the attack failed to eliminate regulation or antitrust entirely, it has proven so enduringly devastating as an intellectual matter that virtually no proposal for government regulation or increased antitrust enforcement is put forward today without an attempt either to justify the proposed departure from an assumed-legitimate free market baseline or to dismiss Chicago School skepticism as an intellectual plot bankrolled by business elites. Chicago School skepticism has been so devastating because it draws sustenance from an inapt metaphor for the economy: that of evolution through natural selection. The free market is, for the Chicago School, nature itself, and all the glories of life suggest that evolution does just fine when left to its own devices, creating a powerful basis for skepticism regarding the need for government intervention in the economy. Except that evolution never did do anything to promote economic growth, so much as theft, a fact that human beings know well given their status as predators of unparalleled success. Humanity did not escape from the subsistence economics that characterizes all of evolved life until humanity started to exert control over the forces of evolution, which is to say: to regulate. A better metaphor for the economy than natural selection is that of a computer running a machine learning algorithm engineered to channel evolutionary forces away from theft and toward growth. The first such algorithm embraced by humanity set evolution aside almost entirely, in favor of identifying optimal productive behaviors directly. That was central planning, which flourished throughout the ancient world and was practiced globally right up to the 19th century. The second such algorithm embraced evolution, but sought to improve upon it by imposing a rule against theft. That was the economic liberalism practiced in the West in the late 19th century. It is also the regime favored by the Chicago School. Approached from the metaphor of the algorithm, the Chicago School’s program appears retrograde, rather than foundational, because it amounts to the position that there should be no version 2.0, no further tweaks to the algorithm. But the antitrust laws, in prohibiting behavior that degrades competitors’ products, even when the behavior does not amount to theft, improves upon the algorithm that is economic liberalism, better channeling life’s evolutionary forces toward productivity and growth, rather than destructive forms of competition.

Abstract 2127: Dissecting the regulatory mechanisms between m6A and alternative splicing: A data-driven study

Abstract N6-methyladenosine (m6A) is the most prevalent modification in the mRNAs, which is a methylated modification on the sixth nitrogen of adenosine. Increasing evidence shows that m6A plays a critical role in many biological processes and diseases including oocyte development, diabetes and cancers. However, the regulation of m6A in the RNA metabolism, especially the relationship between m6A and alternative splicing (AS), remains largely elusive. In this study, we make the first attempt to investigate the underlying regulation relationship between m6A and AS using public resources. We collected both RNA-seq and MeRIP-seq data from HepG2 cell lines with or without METTL14, a methyltransferase, knocked-down. We called differential m6A peaks using an R package named ExomePeak and detected differential alternative splicing events using rMATS software. We considered the AS events overlapped with differential m6A peaks as the regulatory consequence of m6A modification, where we applied GO ontology and pathway enrichment analyses. As the results, we detected 7149 differential genes out of the total 11291 m6A sites. Each differential gene had an average of 1.58 m6A loci. Among these differential m6A genes, 5871 genes were down-regulated and only 2021 genes were up-regulated. We then identified 2465 differential AS events from 1824 unique genes. Skipped exon (SE), the most common type of AS, got 1278 unique genes from 120 events and an average of 1.3 patterns occurred for each gene. For all differentially spliced genes, there were no significant differences between the proportions of up-regulated and down-regulated genes. Next, we intersected total differentially spliced genes with the differential m6A peaks and got 989 differentially m6a-associated spliced genes, which mainly enriched in biological processes including histone modification and intracellular receptor signaling pathway. In addition, by further analyzing the regulatory relationship between m6A and five AS modes, we chose down-regulated m6A genes separately to intersect each AS mode of five. However, we found that the three AS modes, SE, A3SS and A5SS, were more likely co-affected by the knock-down of METTL14. In order to explain this phenomenon, we performed motif analysis on these intersected sequences and compared the enriched motif with known databases. Interestingly, we found that most of the enriched motifs were transcription factor binding. In this work, we explored the role of m6A modification in pre-mRNA splicing. Our results suggested that m6A may have a regulatory role in pre-mRNA splicing, especially ES, A3SS and A5SS modes. Moreover, functional pathway analysis and motif discovery of m6A associated alternative splicing patterns have elucidate the possible mechanisms of m6A in the regulation of biological functions. Citation Format: Lin Wang, Stephen Kwok Wing Tsui. Dissecting the regulatory mechanisms between m6A and alternative splicing: A data-driven study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2127.

Distribution of Risk of Harm in Delictual Responsibility From the Standpoint of Economic Analysis of Law

Damage to property and (or) non-property rights of persons occurs quite often. The right to compensation for such damage is indisputable. However, civil doctrine ambiguously addresses the issue of risk sharing in tort obligations. Therefore, the purpose of this paper is to discuss approaches to the distribution of risk of harm in delictual responsibility and to determine their effectiveness from an economic and legal standpoint. The paper, based on economic and systematic analysis using dialectical, comparative, logical-dogmatic and other methods, including economics, describes the approaches to determining the purpose of tort law and its ability to ensure effective distribution of risk of harm. It has been proven that tort law can have direct regulatory consequences by restraining behaviour and sharing risks. It is concluded that the task of tort law is the optimal distribution of risk of harm between the perpetrator and the victim and to ensure the implementation of risky activities only if its social value justifies the risk. Based on the economic analysis of tort law, it has been substantiated that the distribution of the risk of damage in tort liability is carried out through the institutions of insurance and liability. Insurance is cost-effective when it comes to compensation for damage. However, only liability, in addition to the function of compensation, can also perform the function of preliminary prevention of harm. Therefore, the risk of causing harm in tort liability is mainly borne by the person who caused the damage. In obligations to compensate for damage caused by a source of increased danger, a person who on the appropriate legal basis (property rights, other property rights, contracts, leases, etc.) owns a vehicle, mechanism, other object, the use, storage or maintenance of which creates an increased danger, bears such risk even in the absence of guilt in causing harm. The grounds for imposing such risk on the victim are his intention or force majeure. It is this approach to the distribution of harm risk in tort liability that is fair and cost-effective and contributes to public well-being

Functional annotation of rare structural variation in the human brain

Structural variants (SVs) contribute to many disorders, yet, functionally annotating them remains a major challenge. Here, we integrate SVs with RNA-sequencing from human post-mortem brains to quantify their dosage and regulatory effects. We show that genic and regulatory SVs exist at significantly lower frequencies than intergenic SVs. Functional impact of copy number variants (CNVs) stems from both the proportion of genic and regulatory content altered and loss-of-function intolerance of the gene. We train a linear model to predict expression effects of rare CNVs and use it to annotate regulatory disruption of CNVs from 14,891 independent genome-sequenced individuals. Pathogenic deletions implicated in neurodevelopmental disorders show significantly more extreme regulatory disruption scores and if rank ordered would be prioritized higher than using frequency or length alone. This work shows the deleteriousness of regulatory SVs, particularly those altering CTCF sites and provides a simple approach for functionally annotating the regulatory consequences of CNVs.

The social management of complex uncertainty: Central Bank similarity and crisis liquidity swaps at the Federal Reserve

During the global financial crisis, the Federal Reserve issued billions of dollars in liquidity swap agreements with foreign central banks, serving as a global lender of last resorts. Most studies of this event have analyzed the distribution of these swap lines using materially rational frameworks, which is logical under normal lending conditions. However, this approach does not account for the extensive evidence on social influences over decisions made under uncertainty. Meeting minutes from the Federal Reserve exhibit significant flexibility in recipient selection, and the content of these discussions suggest that social dynamics were important in members’ decision-making. This paper tests the effect of social similarity between foreign central banks and the Federal Reserve on the likelihood of receiving a swap line during the crisis. I introduce new measures of social similarity among central banks with data on employees’ professional ties and public speeches in the years preceding the global financial crisis. Statistical results show a positive, significant effect for social similarity on swap line receipt, even when tested alongside material predictors, and this social rationality appears to have been a deciding feature in some cases of swap distribution. I conclude with implications for future crises, and potential regulatory consequences.

The Redox-Metabolic Couple of T Lymphocytes: Potential Consequences for Hypertension.

Significance: T lymphocytes, as part of the adaptive immune system, possess the ability to activate and function in extreme cellular microenvironments, which requires these cells to remain highly malleable. One mechanism in which T lymphocytes achieve this adaptability is by responding to cues from both reactive oxygen and nitrogen species, as well as metabolic flux, which together fine-tune the functional fate of these adaptive immune cells. Recent Advances: To date, examinations of the redox and metabolic effects on T lymphocytes have primarily investigated these biological processes as separate entities. Given that the redox and metabolic environments possess significant overlaps of pathways and molecular species, it is inevitable that perturbations in one environment affect the other. Recent consideration of this redox-metabolic couple has demonstrated the strong link and regulatory consequences of these two systems in T lymphocytes. Critical Issues: The redox and metabolic control of T lymphocytes is essential to prevent dysregulated inflammation, which has been observed in cardiovascular diseases such as hypertension. The role of the adaptive immune system in hypertension has been extensively investigated, but the understanding of how the redox and metabolic environments control T lymphocytes in this disease remains unclear. Future Directions: Herein, we provide a discussion of the redox and metabolic control of T lymphocytes as separate entities, as well as coupled to one another, to regulate adaptive immunity. While investigations examining this pair together in T lymphocytes are sparse, we speculate that T lymphocyte destiny is shaped by the redox-metabolic couple. In contrast, disrupting this duo may have inflammatory consequences such as hypertension.

Modulation of Peptidoglycan Synthesis by Recycled Cell Wall Tetrapeptides

The bacterial cell wall is made of peptidoglycan (PG), a polymer that is essential for the maintenance of cell shape and survival. During growth, bacteria remodel their PG, releasing fragments that are predominantly re-internalized and recycled. Here, we show that Vibrio cholerae recycles PG fragments modified with non-canonical d-amino acids (NCDAA), which lead to the accumulation of cytosolic PG tetrapeptides. We demonstrate that the accumulation of recycled tetrapeptides has two regulatory consequences for the cell wall: reduction of d,d-cross-linkage and reduction of PG synthesis. We further demonstrate that l,d-carboxypeptidases from five different species show a preferential activity for substrates containing canonical (d-alanine) versus non-canonical (d-methionine) d-amino acids, suggesting that the accumulation of intracellular tetrapeptides in NCDAA-rich environments is widespread. Collectively, this work reveals a regulatory role of NCDAA linking PG recycling and synthesis to promote optimal cell wall assembly and composition in the stationary phase.