Biology subjects

Straesser, K.

Publications and source records attributed to Straesser, K..

4 recordsLinked to original sources

bioRxiv2025

An elevated level of the mRNA exporter Mex67-Mtr2 in nuclear mRNPs impairs nuclear mRNA export

In eukaryotes, a crucial step in gene expression is the export of the mRNA out of nucleus. The conserved mRNA exporter Mex67-Mtr2 (NXF1-NXT1 in human) is a key factor in this process. In S. cerevisiae, it is recruited to the mRNA by the four export adaptors Hpr1, Nab2, Yra1 and Npl3 that play important yet poorly defined roles in nuclear mRNA export. Here, we show that an excess of Mex67 in nuclear mRNPs impairs nuclear mRNA export.{Delta} hpr1 cells have increased Nab2, Yra1 and Mex67 levels in nuclear mRNPs in addition to the export defect. Notably, overexpression of Nab2 or Yra1 in{Delta} hpr1 cells suppresses this export defect and reduces the Mex67 level in nuclear mRNPs to a WT level. Importantly, the increase in the Mex67 level in{Delta} hpr1 cells is not a consequence and thus the cause of the nuclear mRNA export defect. Therefore, precise regulation of the Mex67-Mtr2 level in nuclear mRNPs is essential for efficient nuclear mRNA export.

biochemistry↗

bioRxiv2023

The Prp19C subunits Cwc15 and Syf2 function in TREX occupancy and transcription elongation

The Prp19 complex (Prp19C) is conserved from yeast to human and functions in many different processes such as genome stability, splicing and transcription elongation. In the latter, Prp19C ensures TREX occupancy at transcribed genes. TREX in turn couples transcription to nuclear mRNA export by recruiting the mRNA exporter to transcribed genes and consequently to nascent mRNAs. Here, we assess the function of the nonessential Prp19C subunits Syf2 and Cwc15 in the interaction of Prp19C and TREX with the transcription machinery, Prp19C and TREX occupancy as well as transcription elongation. Whereas both proteins are important for Prp19C-TREX interaction, Syf2 is needed for full Prp19C occupancy, and Cwc15 is important for the interaction of Prp19C with RNA polymerase II and TREX occupancy. These partially overlapping functions are corroborated by a genetic interaction between{Delta} cwc15 and{Delta} syf2. Finally, Cwc15 also interacts genetically with the transcription elongation factor Dst1 and functions in transcription elongation. In summary, we uncover novel roles of the nonessential Prp19C components Syf2 and Cwc15 in Prp19Cs function in transcription elongation.

biochemistry↗

bioRxiv2023

Cross-linking mass spectrometric analysis of the endogenous TREX complex from S. cerevisiae

The conserved TREX complex has multiple functions in gene expression such as transcription elongation, 3 end processing, mRNP assembly and nuclear mRNA export as well as the maintenance of genomic stability. In S. cerevisiae, TREX is composed of the pentameric THO complex, the DEAD-box RNA helicase Sub2, the nuclear mRNA export adaptor Yra1 and the SR-like proteins Gbp2 and Hrb1. Here, we present the structural analysis of the endogenous TREX complex of S. cerevisiae purified from its native environment. To this end, we used cross-linking mass spectrometry to gain structural information on regions of the complex that are not accessible to classical structural biology techniques. We also used negative-stain electron microscopy to investigate the organization of the cross-linked complex used for XL-MS by comparing our endogenous TREX complex with recently published structural models of recombinant THO-Sub2 complexes. According to our analysis, the endogenous yeast TREX complex preferentially assembles into a dimer. The overall structures of the recombinant yeast THO-Sub2 complexes strongly resemble the structural conformation of the monomers and the dimer interface of the endogenous TREX complex.

biochemistry↗

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↗