Dissecting Trypanosoma brucei RRP44 function in the maturation of segmented ribosomal RNA using a regulated genetic complementation system.

Trypanosoma brucei belongs to a group of protozoans presenting fragmented large subunit rRNA. Its LSU rRNA equivalent to the 25S/28S rRNA of other eukaryotes is split into six fragments, requiring additional processing for removal of the extra spacer sequences. We have used a genetic complementation strategy to further investigate the T. brucei RRP44 nuclease in pre-rRNA maturation. TbRRP44 contains both a PIN and a RNB domain whose homologues are found in association with the exosome complex. We found that the exonucleolytic activity of the RNB domain as well as the physical presence of the PIN domain are essential for TbRRP44 function, while a catalytic site mutation in the PIN domain has no detectable effect on cell growth. A new endonucleolytic cleavage site in ITS1 was identified. In addition to the 5.8S rRNA 3'-end maturation, TbRRP44 is required for degradation of the excised 5'-ETS and for removal of part of ITS1 during maturation of the 18S rRNA 3'-end. TbRRP44 deficiency leads to accumulation of many LSU intermediate precursors, most of them not detected in control cells. TbRRP44 is also required for U3 snoRNA and spliced leader processing, indicating that TbRRP44 may have a wide role in RNA processing in T. brucei.

Trypanosoma brucei RRP44: a versatile enzyme for processing structured and non-structured RNA substrates.

Rrp44/Dis3 is a conserved eukaryotic ribonuclease that acts on processing and degradation of nearly all types of RNA. It contains an endo- (PIN) and an exonucleolytic (RNB) domain and, its depletion in model organisms supports its essential function for cell viability. In Trypanosoma brucei, depletion of Rrp44 (TbRRP44) blocks maturation of ribosomal RNA, leading to disruption of ribosome synthesis and inhibition of cell proliferation. We have determined the crystal structure of the exoribonucleolytic module of TbRRP44 in an active conformation, revealing novel details of the catalytic mechanism of the RNB domain. For the first time, the position of the second magnesium involved in the two-metal-ion mechanism was determined for a member of the RNase II family. In vitro, TbRRP44 acts preferentially on non-structured uridine-rich RNA substrates. However, we demonstrated for the first time that both TbRRP44 and its homologue from Saccharomyces cerevisiae can also degrade structured substrates without 3'-end overhang, suggesting that Rrp44/Dis3 ribonucleases may be involved in degradation of a wider panel of RNA than has been assumed. Interestingly, deletion of TbRRP44 PIN domain impairs RNA binding to different extents, depending on the type of substrate.

Patterns of Care for Breast Radiotherapy in Italy: Breast IRRadiATA (Italian Repository of Radiotherapy dATA) Feasibility Study.

Aim. Breast IRRADIATA (Italian Repository of RADIotherapy dATA) is a collaborative nationwide project supported by the Italian Society of Radiotherapy and Clinical Oncology (AIRO) and the Italian League Against Cancer (LILT). It focuses on breast cancer (BC) patients treated with radiotherapy (RT) and was developed to create a national registry and define the patterns of care in Italy. A dedicated tool for data collection was created and pilot tested. The results of this feasibility study are reported here. Methods. To validate the applicability of a user-friendly data collection tool, a feasibility study involving 17 Italian Radiation Oncology Centers was conducted from July to October 2021, generating a data repository of 335 BC patients treated between January and March 2020, with a minimum follow-up time of 6 months. A snapshot of the clinical presentation, treatment modalities and radiotherapy toxicity in these patients was obtained. A Data Entry Survey and a Satisfaction Questionnaire were also sent to all participants. Results. All institutions completed the pilot study. Regarding the Data Entry survey, all questions achieved 100% of responses and no participant reported spending more than 10 min time for either the first data entry or for the updating of follow-up. Results from the Satisfaction Questionnaire revealed that the project was described as excellent by 14 centers (82.3%) and good by 3 (17.7%). Conclusion. Current knowledge for the treatment of high-prevalence diseases, such as BC, has evolved toward patient-centered medicine, evidence-based care and real-world evidence (RWE), which means evidence obtained from real-world data (RWD). To this aim, Breast IRRADIATA was developed as a simple tool to probe the current pattern of RT care in Italy. The pilot feasibility of IRRADIATA encourages a larger application of this tool nationwide and opens the way to the assessment of the pattern of care radiotherapy directed to other cancers.

Trypanosoma brucei RRP44 is involved in an early stage of large ribosomal subunit RNA maturation.

Ribosomal RNA precursors undergo a series of structural and chemical modifications to generate matured RNA molecules that will comprise ribosomes. This maturation process involves a large set of accessory proteins as well as ribonucleases, responsible for removal of the external and internal transcribed spacers from the pre-rRNA. Early-diverging eukaryotes belonging to the Kinetoplastida class display several unique characteristics, in particular in terms of RNA synthesis and maturation. These peculiarities include the rRNA biogenesis and the extensive fragmentation of the large ribosomal subunit (LSU) rRNA. The role of specific endo- and exonucleases in the maturation of the unusual rRNA precursor of trypanosomatids remains largely unknown. One of the nucleases involved in rRNA processing is Rrp44, an exosome associated ribonuclease in yeast, which is involved in several metabolic RNA pathways. Here, we investigated the function of Trypanosoma brucei RRP44 orthologue (TbRRP44) in rRNA processing. Our results revealed that TbRRP44 depletion causes unusual polysome profile and accumulation of the complete LSU rRNA precursor, in addition to 5.8S maturation impairment. We also determined the crystal structure of TbRRP44 endonucleolytic domain. Structural comparison with Saccharomyces cerevisiae Rrp44 revealed differences in the catalytic site and substitutions of surface residues, which could provide molecular bases for the lack of interaction of RRP44 with the exosome complex in T. brucei.