Biology subjects

Höfer, K.

Publications and source records attributed to Höfer, K..

5 recordsLinked to original sources

bioRxiv2025

Engineering site-specific nucleic acid-protein conjugates by utilizing a natural RNAylation reaction

Nucleic acid-protein conjugates are valuable for synthetic biology, therapeutics, and nanotechnology, but current methods often lack site specificity and rely on non-natural linkages. RNAylation, a one-step enzymatic reaction catalyzed by the bacteriophage T4 enzyme ModB where first discovered in vivo during phage infection, enables site-specific conjugation of nucleic acids to proteins via a natural N-glycosidic bond. Here, we establish RNAylation as a novel and robust in vitro platform for generating nucleic acid-protein conjugates, overcoming key limitations of existing strategies. We define design principles for this approach, demonstrate enhanced nucleic acid stability in human cell lysates, and develop an efficient purification workflow. Furthermore, we achieve successful delivery of purified conjugates into human cells, highlighting the potential for functional in vivo applications. Our work expands RNAylation from a phage-specific phenomenon to a versatile, biologically relevant strategy with broad biotechnological potential.

bioengineering↗

bioRxiv2025

Proteins are a source of glycans found in preparations of glycoRNA

Recent discoveries show that RNA can be modified with sialylated glycans (termed glycoRNA), thus broadening our understanding of cellular glycosylation beyond traditional proteins and lipids. However, the pathway of RNA-glycosylation and its biological function remain elusive. Following the original glycoRNA isolation protocol, we also detect labelled glycans in small RNA preparations. However, glycosylated molecules showed resistance to treatment with RNase A/T1 but were sensitive to proteinase K digestion under denaturing conditions. Using liquid chromatography-mass spectrometry (LC-MS) based proteomics, we detect various proteins that co-purify with small but not large RNA preparations isolated from human or murine cells, including the glycosylated membrane protein LAMP1. Importantly, we further demonstrate that recombinant soluble LAMP1 can be purified following the glycoRNA isolation method. These findings suggest that glycoproteins co-purify with RNA using current glycoRNA purification protocols, thus representing a considerable source of glycans in samples of glycoRNA.

molecular biology↗

bioRxiv2024

T4 phage RNA is NAD-capped and alters the NAD-capepitranscriptome of Escherichia coli during infection through a phage-encoded decapping enzyme

Nicotinamide adenine dinucleotide (NAD+) serves as a cap-like structure on cellular RNAs (NAD-RNAs) across all domains of life, including Escherichia coli. Beyond its role in metabolism, NAD+ also functions as a regulatory molecule in phage defense mechanisms. However, NAD-RNAs have not yet been identified during bacteriophage infections, and the mechanisms governing their synthesis and degradation in this context remain unknown. To address this gap, we used T4 phage infection of E. coli as a defined and well-characterized model system to study NAD-RNAs at the virus-host interface. Here, we report the first identification and characterization of NAD-RNAs during phage infection. Using time-resolved NAD captureSeq, we identified NAD-capped host and T4 phage transcripts and observed that the set of enriched NAD-capped RNAs varies across different infection phases. Importantly, NAD captureSeq identifies NAD-capped transcripts based on enrichment and does not directly report the fraction of molecules that are NAD-capped. Consequently, temporal changes in enrichment may reflect altered NAD-capping, altered transcript abundance, or a combination of both. We provide evidence that NAD-RNAs are generated by the host RNA polymerase by initiating transcription with NAD+ at canonical transcription start sites. By quantifying intracellular NAD+ and bulk NAD-capped RNA during infection, we observe parallel decreases in both parameters over the course of infection. Furthermore, we characterize NudE.1, a T4 phage-encoded Nudix hydrolase previously shown to have in vitro NAD-RNA decapping activity. Together, our work presents the first time-resolved analysis of an RNA modification in a host-phage system, defining the landscape, dynamics, and turnover of NAD-capped RNAs during infection and providing a framework for future studies addressing their regulatory functions in phage biology.

microbiology↗

bioRxiv2024

Temporal epigenome modulation enables efficient bacteriophage engineering and functional analysis of phage DNA modifications

Lytic bacteriophages hold substantial promise in medical and biotechnological applications. CRISPR-Cas systems offer a way to explore these mechanisms via site-specific phage mutagenesis. However, phages can resist Cas-mediated cleavage through extensive DNA modifications like cytosine glycosylation, hindering mutagenesis efficiency. Our study utilizes the eukaryotic enzyme NgTET to temporarily reduce phage DNA modifications, facilitating Cas nuclease cleavage and enhancing mutagenesis efficiency. This approach enables precise DNA targeting and seamless point mutation integration, exemplified by deactivating specific ADP-ribosyltransferases crucial for phage infection. Furthermore, by temporally removing DNA modifications, we elucidated the effects of these modifications on T4 phage infections without necessitating gene deletions. Our results present a strategy enabling the investigation of phage epigenome functions and streamlining the engineering of phages with cytosine DNA modifications. The described temporal modulation of the phage epigenome is valuable for synthetic biology and fundamental research to comprehend phage infection mechanisms through the generation of mutants.

microbiology↗

bioRxiv2022

Identification of NAD-RNAs and ADPR-RNA decapping in the archaeal model organisms Sulfolobus acidocaldarius and Haloferax volcanii

NAD is a coenzyme central to metabolism that was also found to serve as a 5-terminal cap of bacterial and eukaryotic RNA species. The presence and functionality of NAD-capped RNAs (NAD-RNAs) in the archaeal domain remain to be characterized in detail. Here, by combining LC-MS and NAD captureSeq methodology, we quantified the total levels of NAD-RNAs and determined the identity of NAD-RNAs in the two model archaea, Sulfolobus acidocaldarius and Haloferax volcanii. A complementary differential RNA-Seq (dRNA-Seq) analysis revealed that NAD transcription start sites (NAD-TSS) correlate with well-defined promoter regions and often overlap with primary transcription start sites (pTSS). The population of NAD-RNAs in the two archaeal organisms shows clear differences, with S. acidocaldarius possessing more capped small non-coding RNAs (sncRNAs) and leader sequences. The NAD-cap did not prevent 5[->]3 exonucleolytic activity by the RNase Saci-aCPSF2. To investigate enzymes that facilitate the removal of the NAD-cap, four Nudix proteins of S. acidocaldarius were screened. None of the recombinant proteins showed NAD decapping activity. Instead, the Nudix protein Saci_NudT5 showed activity after incubating NAD-RNAs at elevated temperatures. Hyperthermophilic environments promote the thermal degradation of NAD into the toxic product ADPR. Incorporating NAD into RNAs and the regulation of ADPR-RNA decapping by Saci_NudT5 is proposed to provide additional layers of maintaining stable NAD levels in archaeal cells. ImportanceThis study reports the first characterization of 5-terminally modified RNA molecules in Archaea and establishes that NAD-RNA modifications, previously only identified in the other two domains of life, are also prevalent in the archaeal model organisms Sulfolobus acidocaldarius and Haloferax volcanii. We screened for NUDIX hydrolases that could remove the NAD-RNA cap and showed that none of these enzymes removed NAD modifications, but we discovered an enzyme that hydrolyzes ADPR-RNA. We propose that these activities influence the stabilization of NAD and its thermal degradation to potentially toxic ADPR products at elevated growth temperatures.

molecular biology↗