PubMed · 14352041
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E S DOWDING, A BAKERSPIGEL. 1954. The migrating nucleus.. https://doi.org/10.1139/m55-010
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In this issue of Cell Genomics, McKeever et al.1 generate a single-nucleus transcriptomic atlas of ALS/FTLD brain and reveal widespread alternative polyadenylation changes. Their findings highlight 3' end RNA processing as a central integrator of stress responses, cell-type specificity, and disease susceptibility, offering new mechanistic insight and potential therapeutic directions.
The nuclear-encoded protein RPS14 (ribosomal protein S14) of rice mitochondria is synthesized in the cytosol as a polyprotein consisting of a large N-terminal domain comprising preSDHB (succinate dehydrogenase B precursor) and the C-terminal RPS14. After the preSDHB-RPS14 polyprotein is transported into the mitochondrial matrix, the protein is processed into three peptides: the N-terminal prepeptide, the SDHB domain and the C-terminal mature RPS14. Here we report that the general MPP (mitochondrial processing peptidase) plays an essential role in processing of the polyprotein. Purified yeast MPP cleaved both the N-terminal presequence and the connector region between SDHB and RPS14. Moreover, the connector region was processed more rapidly than the presequence. When the site of cleavage between SDHB and RPS14 was determined, it was located in an MPP processing motif that has also been shown to be present in the N-terminal presequence. Mutational analyses around the cleavage site in the connector region suggested that MPP interacts with multiple sites in the region, possibly in a similar manner to the interaction with the N-terminal presequence. In addition, MPP preferentially recognized the unfolded structure of preSDHB-RPS14. In mitochondria, MPP may recognize the stretched polyprotein during passage of the precursor through the translocational apparatus in the inner membrane, and cleave the connecting region between the SDHB and RPS14 domains even before processing of the presequence.
Beta-catenin is a crucial part of the Wnt and E-cadherin signalling pathways, which are involved in tumorigenesis. Dysregulation of these pathways allow beta-catenin to accumulate and translocate to the nucleus, where it may activate oncogenes. Such nuclear accumulation can be detected by immunohistochemistry, which may be useful in diagnosis. Although the role of beta-catenin has been established in various types of carcinomas, relatively little is known about its status in mesenchymal tumors. A number of studies suggest that beta-catenin dysregulation is important in desmoid-type fibromatosis, as well as in synovial sarcoma. We wished to determine whether nuclear beta-catenin expression is specific to and sensitive for particular bone and soft-tissue tumors, including sporadic desmoid-type fibromatosis. We studied the nuclear expression of beta-catenin using tissue microarrays in a comprehensive range of bone and soft-tissue tumor types. A total of 549 cases were included in our panel. Nuclear immunohistochemical staining was determined to be either high level (>25% of cells), low level (0-25%) or none. High-level nuclear beta-catenin staining was seen in a very limited subset of tumor types, including desmoid-type fibromatosis (71% of cases), solitary fibrous tumor (40%), endometrial stromal sarcoma (40%) and synovial sarcoma (28%). Although occasional cases of fibrosarcoma, clear cell sarcoma and carcinosarcoma had high-level staining, no high-level nuclear beta-catenin expression was seen in any of 381 fibrohistocytic, muscular, adipocytic, chondroid or osseous tumor cases representing 42 diagnostic categories. All primary immunostain tissue microarray images are made publicly accessible in a searchable database. High-level nuclear beta-catenin staining serves as a useful diagnostic tool, as it is specific to a small subset of mesenchymal tumors.