RESUMO
Loss of heterozygosity in the SMARCA4 gene is a hallmark feature of small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), an aggressive ovarian cancer occurring in young adults and adolescents with an average age of 23 years and a median survival of less than fifteen months following diagnosis. Patients with germline pathogenic variants of SMARCA4 have a genetic predisposition to developing this aggressive ovarian cancer, a condition called rhabdoid tumor predisposition syndrome type 2 (RTPS2). Given the limited efficacy of surveillance imaging for ovarian neoplasm and the absence of an identified biomarker for the progression of this disease, asymptomatic patients who are found to possess pathogenic variants of the SMARCA4 gene following genetic testing are advised to consider risk-reducing bilateral salpingo-oophorectomy to eliminate the risk of SCCOHT. Given the reproductive impacts of this procedure, bioethical consultation must be considered when counseling patients with RTPS2, particularly for those who have not completed their desired course of family planning. In this report, we describe the bioethical considerations and outcomes for the case of a 6-year-old female with a pathogenic variant of SMARCA4 who underwent risk-reducing bilateral salpingo-oophorectomy (RRBSO). To our knowledge, this is the first time that this procedure has been reported in a prepubertal individual for cancer prevention in a patient with RTPS2.
RESUMO
Faithful translation of the genetic code is critical for the viability of all living organisms. The trans-editing enzyme ProXp-ala prevents Pro to Ala mutations during translation by hydrolyzing misacylated Ala-tRNAPro that has been synthesized by prolyl-tRNA synthetase. Plant ProXp-ala sequences contain a conserved C-terminal domain (CTD) that is absent in other organisms; the origin, structure, and function of this extra domain are unknown. To characterize the plant-specific CTD, we performed bioinformatics and computational analyses that provided a model consistent with a conserved α-helical structure. We also expressed and purified wildtype Arabidopsis thaliana (At) ProXp-ala in Escherichia coli, as well as variants lacking the CTD or containing only the CTD. Circular dichroism spectroscopy confirmed a loss of α-helical signal intensity upon CTD truncation. Size-exclusion chromatography with multiangle laser-light scattering revealed that wildtype At ProXp-ala was primarily dimeric and CTD truncation abolished dimerization in vitro. Furthermore, bimolecular fluorescence complementation assays in At protoplasts support a role for the CTD in homodimerization in vivo. The deacylation rate of Ala-tRNAPro by At ProXp-ala was also significantly reduced in the absence of the CTD, and kinetic assays indicated that the reduction in activity is primarily due to a tRNA binding defect. Overall, these results broaden our understanding of eukaryotic translational fidelity in the plant kingdom. Our study reveals that the plant-specific CTD plays a significant role in substrate binding and canonical editing function. Through its ability to facilitate protein-protein interactions, we propose the CTD may also provide expanded functional potential for trans-editing enzymes in plants.
