Biology subjects

Wulf, A.

Publications and source records attributed to Wulf, A..

4 recordsLinked to original sources

bioRxiv2024

Chemical crosslinking extends and complements UV crosslinking in analysis of RNA/DNA nucleic acid-protein interaction sites by mass spectrometry

UV (ultra-violet) crosslinking with mass spectrometry (XL-MS) has been established for identifying RNA- and DNA-binding proteins along with their domains and amino acids involved. Here, we explore chemical XL-MS for RNA-protein, DNA-protein, and nucleotide-protein complexes in vitro and in vivo. We introduce a specialized nucleotide-protein-crosslink search engine, NuXL, for robust and fast identification of such crosslinks at amino acid resolution. Chemical XL-MS complements UV XL-MS by generating different crosslink species, increasing crosslinked protein yields in vivo almost four-fold, and thus it expands the structural information accessible via XL-MS. Our workflow facilitates integrative structural modelling of nucleic acid-protein complexes and adds spatial information to the described RNA-binding properties of enzymes, for which crosslinking sites are often observed close to their cofactor-binding domains. In vivo UV and chemical XL-MS data from E. coli cells analysed by NuXL establish a comprehensive nucleic acid-protein crosslink inventory with crosslink sites at amino acid level for more than 1500 proteins. Our new workflow combined with the dedicated NuXL search engine identified RNA crosslinks that cover most RNA-binding proteins, with DNA and RNA crosslinks detected in transcriptional repressors and activators.

biochemistry↗

bioRxiv2023

Control of a type III-Dv CRISPR-Cas system by the transcription factor RpaB and interaction of its transcribed leader with the DEAD-box RNA helicase CrhR

CRISPR-Cas systems in bacteria and archaea provide powerful defense against phages and other foreign genetic elements. The principles of CRISPR-Cas activity are well understood, but less is known about how their expression is regulated. The cyanobacterium Synechocystis sp. PCC 6803 encodes three different CRISPR-Cas systems. The expression of one of these, a type III-Dv system, responds to changes in environmental conditions, such as nitrogen starvation or varying light intensities. Here, we found that the promoter of the six-gene cas operon for the type III-Dv system is controlled by the light-and redox-responsive transcription factor RpaB. RpaB binds to an HLR1 motif located 53 to 70 nt upstream of the transcription start site, resulting in transcriptional activation at low light intensities. However, the strong promoter that drives transcription of the cognate repeat-spacer array is not controlled by RpaB. Instead, we found that the 125 nt leader transcript is bound by the redox-sensitive RNA helicase CrhR. Crosslinking coupled to mass spectrometry analysis revealed six residues involved in the CrhR-RNA interaction. Of these, L103, F104, H225, and C371 were predicted to be on the surface of a dimeric CrhR model, while C184 was not on the surface, and P443 could not be assigned to a structural element. These results showed that the expression of the CRISPR-Cas system is linked to the redox status of the photosynthetic cyanobacterial cell at two different levels. While RpaB affects transcription, CrhR interacts with the leader transcript posttranscription. These results highlight the complex interplay between a CRISPR-Cas system and its host cell.

microbiology↗

bioRxiv2022

Npl3 functions in mRNP assembly by recruitment of mRNP components to the transcription site and their transfer onto the mRNA

RNA-binding proteins (RBPs) control every RNA metabolic process by multiple protein-RNA and protein-protein interactions. Their roles have largely been analyzed by crude mutations, which abrogate multiple functions at once and likely impact the structural integrity of the large messenger ribonucleoprotein particle (mRNP) assemblies, these proteins often function in. Using UV-induced RNA-protein crosslinking and subsequent mass spectrometric analysis, we first identified more than 100 in vivo RNA crosslinks in 16 nuclear mRNP components in S. cerevisiae. For functional analysis, we chose Npl3, for which we determined crosslinks in its two RNA recognition motifs (RRM) and in the flexible linker region connecting the two. Using NMR and structural analyses, we show that both RRM domains and the linker uniquely contribute to RNA recognition. Interestingly, mutations in these regions cause different phenotypes, indicating distinct functions of the different RNA-binding domains of Npl3. Notably, the npl3-Linker mutation strongly impairs recruitment of several mRNP components to chromatin and incorporation of further mRNP components into nuclear mRNPs, establishing a function of Npl3 in nuclear mRNP assembly. Taken together, we determined the specific function of the RNA-binding activity of the nuclear mRNP component Npl3, an approach that can be applied to many RBPs in any RNA metabolic process.

biochemistry↗

bioRxiv2021

Viral ADP-ribosyltransferases attach RNA chains to host proteins

The mechanisms by which viruses hijack their hosts genetic machinery are of current interest. When bacteriophage T4 infects Escherichia coli, three different ARTs (ADP-ribosyltransferases) reprogram the hosts transcriptional and translational apparatus through ADP-ribosylation using nicotinamide adenine dinucleotide (NAD) as substrate 1,2. Recently, NAD was identified as a 5-modification of cellular RNAs 3-5. Here, we report that T4 ART ModB accepts not only NAD but also NAD-capped RNA (NAD-RNA) as substrate and attaches entire RNA chains to acceptor proteins in an "RNAylation" reaction. ModB specifically RNAylates ribosomal proteins rS1 and rL2 at defined arginine residues, and a specific group of E. coli and T4 phage RNAs is linked to rS1 in vivo. T4 phages that express an inactive mutant of ModB show a decreased burst size and slowed lysis of E. coli. Our findings reveal a distinct biological role of NAD-RNA, namely activation of the RNA for enzymatic transfer to proteins. The attachment of specific RNAs to ribosomal proteins might provide a strategy for the phage to modulate the hosts translation machinery. This work exemplifies the first direct connection between RNA modification and post-translational protein modification. As ARTs play important roles far beyond viral infections 6, RNAylation may have far-reaching implications.

microbiology↗