Summary RNA-binding proteins (RBPs) are typically involved in non-equilibrium cellular processes, and specificity can arise from differences in ground state, transition state or product states of the binding reactions for alternative RNAs. Here, we use high throughput methods to measure and analyze the RNA association kinetics and equilibrium binding affinity for all possible sequence combinations in precursor tRNA binding site of C5, the essential protein subunit of Escherichia coli ribonuclease P. The results show that the RNA sequence specificity of C5 arises due to favorable RNA-protein interactions that stabilize the transition state for association and bound ES complex. Specificity is further impacted by unfavorable RNA structure involving the C5 binding site in the ground state. The results illustrate a comprehensive quantitative approach for analysis of RNA binding specificity, and show how both RNA structure and sequence preferences of an essential protein subunit direct the specificity of a ribonucleoprotein enzyme.

Binding of precursor tRNAs (ptRNAs) by bacterial ribonuclease P (RNase P) involves an encounter complex (ES) that isomerizes to a catalytic conformation (ES*). However, the structures of intermediates and the conformational changes that occur during binding are poorly understood. Here, we show that pairing between the 5′ leader and 3′RCCA extending the acceptor stem of ptRNA inhibits ES* formation. Cryo-electron microscopy single particle analysis reveals a dynamic enzyme that becomes ordered upon formation of ES* in which extended acceptor stem pairing is unwound. Comparisons of structures with alternative ptRNAs reveals that once unwinding is completed RNase P primarily uses stacking interactions and shape complementarity to accommodate alternative sequences at its cleavage site. Our study reveals active site interactions and conformational changes that drive molecular recognition by RNase P and lays the foundation for understanding how binding interactions are linked to helix unwinding and catalysis.

POI should be suspected in pediatric surgical patients who showed signs of intestinal obstruction in the early postoperative period. Early recognition and prompt management are important.

Giant cell tumors (GCTs) mainly occur in metaphyses of long bones and are generally considered histologically benign; however, GCTs may be locally aggressive with a high rate of local recurrence and exhibit the potential for distant metastasis. Primary GCT of the clivus is extremely rare and is easily misdiagnosed and, thus, treatment remains controversial. The present report describes the case of a 22-year-old male with GCT located in the skull base originating from the clivus, with the involvement of multiple cranial nerves, which was successfully treated with transnasal transsphenoidal surgery following adjuvant radiotherapy and intravenous bisphosphonate administration. The patient remains symptom free at two years of follow-up. This report contributes to the limited literature regarding GCTs of the skull.