A cell-permeable Ub-Dha probe for profiling E1-E2-E3 enzymes in live cells.

Activity-based ubiquitin probes (Ub-ABPs) have recently been developed as effective tools for studying the capabilities of E1-E2-E3 enzymes, but most of them can only be used in cell lysates. Here, we report the first cell-penetrating Ub-Dha probes based on thiazolidine-protected cysteines, which enable successful delivery into cells confirmed by a fluorophore at the N-terminus of Ub and live-cell fluorescence microscopy. A total of 18 E1-E2-E3 enzymes in live cells were labelled and enriched in combination with label-free quantification (LFQ) mass spectrometry. This work provided a new cell-penetrating Ub tool for studying the activity and function of Ub-related enzymes.

A detection model of testis-derived circular RNAs in serum for predicting testicular sperm retrieval rate in non-obstructive azoospermia patients.

BACKGROUND: Microdissection testicular sperm extraction is an effective method to retrieve sperm from non-obstructive azoospermia patients. However, its successful rate is less than 50%. OBJECTIVES: To identify the predictive value of circular RNAs in serum for sperm retrieval rate in non-obstructive azoospermia patients. MATERIALS AND METHODS: 180 non-obstructive azoospermia patients were recruited in this study, including 84 individuals with successful sperm retrieval and 96 individuals with failed sperm retrieval. Our study contained two phases. First, 20 patients, selected from the 180 patients, were included in screening cohort. In this cohort, the top 20 circular RNAs from our previous testicular circRNA profiles were verified between successful and failed sperm retrieval groups using real-time polymerase chain reaction. Six circular RNAs with the most significantly different expressions were selected for further verification. Second, the 180 patients were included as discovery cohort to verify the six circular RNAs. Circular RNAs were extracted from serum in each participant. Logistic regression analysis was further performed to identify the predictive value and the area under the curve analysis was used to evaluate diagnostic efficiency, sensitivity, and specificity. RESULTS: Six circular RNAs including hsa_circ_0058058, hsa_circ_0008045, hsa_circ_0084789, hsa_circ_0000550, hsa_circ_0007422, and hsa_circ_0004099 showed aberrant expressions between the successful and failed sperm retrieval group. In addition, both single-circular RNA panels and multi-circular RNA panels were finally verified to be significant in predicting sperm retrieval rate. Notably, multi-circular RNAs panels demonstrated better predictive abilities compared with single-circRNA panels, and the combined panel of six-circular RNAs (risk score = 1.094×hsa_circ_0058058+0.697×hsa_circ_0008045+0.718×hsa_circ_0084789-0.591×hsa_circ_0000550-0.435×hsa_circ_0007422-1.017×hsa_circ_0004099-1.561) exhibited the best predictive ability in the present study with an AUC of 0.977, a sensitivity of 91.7% and a specificity of 86.5%. A higher risk score indicated a higher risk of failure in sperm retrieval. DISCUSSION AND CONCLUSION: Our study was the first to report that testis-derived circular RNAs in serum have the ability to predict sperm retrieval rate in non-obstructive azoospermia patients, whether it is a single-circular RNA or a combination of multi-circular RNAs.

Acyl azide modification of the ubiquitin C-terminus enables DUB capture.

Deubiquitinating enzyme (DUB) abnormalities are associated with many diseases. Previous attempts have been made to introduce various chemical groups such as alkynes, unsaturated olefins and alkyl halides to the C-terminus of ubiquitin (Ub) to capture the active-site cysteine residue in DUBs for structural and biochemical studies. Here, we find that a Ub C-terminal acyl azide can capture DUBs, thereby forming thioester bonds in buffers and cell lysates. This finding not only makes ubiquitin acyl azide a chemical probe for capturing DUBs, but also extends the utility of azide groups in biological applications.