Biology subjects

Hayne, C. K.

Publications and source records attributed to Hayne, C. K..

4 recordsLinked to original sources

bioRxiv2025

Biochemical characterizations of Pontocerebellar Hypoplasia linked mutations of Target of Egr1 (TOE1) reveal impacts on thermal stability, ribonuclease activity, and oligomerization

The Target of EGR1 (TOE1) gene encodes the TOE1 deadenylase, which is essential for the maturation of Pol-II transcribed snRNAs in humans. Over a dozen missense mutations in the TOE1 gene have been linked to Pontocerebellar Hypoplasia Type 7 (PCH7), a rare but serious neurodevelopmental and neurodegenerative disease that leads to early mortality. The biochemical mechanisms for why these PCH7-linked mutations alter TOE1s biochemical characteristics remains vague. Here, we utilized AlphaFold predicted structures of TOE1 and biochemical characterizations to investigate the impact of selected TOE1 variants on TOE1s biochemical properties. We performed characterization of the thermal stability and activity of eleven PCH-linked TOE1 variants and found that eight variants have significantly reduced protein thermal stability and that all but two variants impair TOE1s ribonuclease activity, particularly its exonuclease activity. Additionally, we found that the F148Y mutation impacts TOE1s oligomeric state in vitro and in vivo. Together, these results demonstrate that PCH-linked mutations of TOE1 impact many different aspects of TOE1 biochemistry, providing novel insights which may provide potential therapeutic strategies to treat PCH7 patients. In addition, these mutations provide a library of TOE1 variants that will be useful for future studies of TOE1 function and regulation.

biochemistry↗

bioRxiv2022

Structural Basis for pre-tRNA Recognition and Processing by the Human tRNA Splicing Endonuclease Complex

Across all walks of life, certain transfer RNA (tRNA) transcripts contain introns. Pre-tRNAs with introns require splicing to form the mature anticodon stem loop (ASL). In eukaryotes, tRNA splicing is initiated by the heterotetrameric tRNA splicing endonuclease (TSEN) complex. All TSEN subunits are essential and mutations within the complex are associated with a family of neurodevelopmental disorders known as pontocerebellar hypoplasia (PCH). The pathogenesis of PCH is poorly understood. Moreover, a lack of structures for any eukaryotic TSEN complex has hindered our understanding of tRNA recognition and processing. Here, we report Cryo-Electron Microscopy (cryo-EM) structures of the human TSEN*pre-tRNA complex, trapped in the pre-cleavage state, at near atomic resolution. These structures reveal the overall architecture of the complex, along with extensive tRNA binding interfaces within the complex. Although it shares structural homology with archaeal TSENs, the human TSEN complex contains additional features important for recognizing the acceptor stem and D-arm of the pre-tRNA. Our findings also establish the TSEN54 subunit as more than a simple molecular ruler; it functions as a pivotal scaffold for the pre-tRNA and the two endonuclease subunits, TSEN2 and TSEN34. Finally, the human TSEN structures enable detailed visualization of the molecular environments of PCH-causing missense mutations, providing crucial insight into the mechanism of eukaryotic pre-tRNA splicing and neurodevelopmental disease.

biochemistry↗

bioRxiv2020

Cryo-EM Structures of the SARS-CoV-2 Endoribonuclease Nsp15

New therapeutics are urgently needed to inhibit SARS-CoV-2, the virus responsible for the on-going Covid-19 pandemic. Nsp15, a uridine-specific endoribonuclease found in all coronaviruses, processes viral RNA to evade detection by RNA-activated host defense systems, making it a promising drug target. Previous work with SARS-CoV-1 established that Nsp15 is active as a hexamer, yet how Nsp15 recognizes and processes viral RNA remains unknown. Here we report a series of cryo-EM reconstructions of SARS-CoV-2 Nsp15. The UTP-bound cryo-EM reconstruction at 3.36 [A] resolution provides molecular details into how critical residues within the Nsp15 active site recognize uridine and facilitate catalysis of the phosphodiester bond, whereas the apo-states reveal active site conformational heterogeneity. We further demonstrate the specificity and mechanism of nuclease activity by analyzing Nsp15 products using mass spectrometry. Collectively, these findings advance understanding of how Nsp15 processes viral RNA and provide a structural framework for the development of new therapeutics.

biochemistry↗

bioRxiv2019

Reconstitution of the Human tRNA Splicing Endonuclease Complex: insight into the regulation of pre-tRNA cleavage.

The splicing of tRNA introns is a critical step in pre-tRNA maturation. In archaea and eukaryotes, tRNA intron removal is catalyzed by the tRNA splicing endonuclease (TSEN) complex. Eukaryotic TSEN is comprised of four core subunits (TSEN54, TSEN2, TSEN34, and TSEN15). The human TSEN complex additionally co-purifies with the polynucleotide kinase CLP1; however, CLP1s role in tRNA splicing remains unclear. Mutations in genes encoding all four TSEN subunits, as well as CLP1, are known to cause neurodegenerative disorders, yet the mechanisms underlying the pathogenesis of these disorders are unknown. Here, we developed a recombinant system that produces active TSEN complex. Co-expression of all four TSEN subunits is required for efficient formation and function of the complex. We show that human CLP1 associates with the active TSEN complex, but is not required for tRNA intron cleavage in vitro. Moreover, RNAi knockdown of the Drosophila CLP1 orthologue, cbc, promotes biogenesis of mature tRNAs and circularized tRNA introns (tricRNAs) in vivo. Collectively, these and other findings suggest that CLP1/cbc plays a regulatory role in tRNA splicing by serving as a negative modulator of the direct tRNA ligation pathway in animal cells.

molecular biology↗