We constructed a regulation system for DNA secondary structure formation of G-rich sequences using a designed PNA peptide exhibiting an on-to-off switching functionality, depending on the protease activity. This study introduces the new concept of a simple and powerful system for regulating quadruplex-related important biological events.

The development of a switching system for guanine nanowire (G-wire) formation by external signals is important for nanobiotechnological applications. Here, we demonstrate a DNA nanostructural switch (G-wire <--> particles) using a designed peptide and a protease. The peptide consists of a PNA sequence for inducing DNA to form DNA–PNA hybrid G-quadruplex structures, and a protease substrate sequence acting as a switching module that is dependent on the activity of a particular protease. Micro-scale analyses via TEM and AFM showed that G-rich DNA alone forms G-wires in the presence of Ca2+, and that the peptide disrupted this formation, resulting in the formation of particles. The addition of the protease and digestion of the peptide regenerated the G-wires. Macro-scale analyses by DLS, zeta potential, CD, and gel filtration were in agreement with the microscopic observations. These results imply that the secondary structure change (DNA G-quadruplex <--> DNA/PNA hybrid structure) induces a change in the well-formed nanostructure (G-wire <--> particles). Our findings demonstrate a control system for forming DNA G-wire structures dependent on protease activity using designed peptides. Such systems hold promise for regulating the formation of nanowire for various applications, including electronic circuits for use in nanobiotechnologies.

PurposeTo report a rare case of primary orbital natural killer (NK)/T-cell lymphoma without nasal lesions but with cerebrospinal fluid involvement.ObservationsA 73-year-old woman was referred to the uveitis clinic with suspected unilateral acute uveitis in her right eye and a right orbital tumor. Epstein–Barr virus DNA was detected in the aqueous humor in her right eye, and orbital biopsy revealed the presence of extranodal NK/T-cell lymphoma (ENKTL), nasal type. Positron emission tomography showed significant 18F-fluorodeoxyglucose uptake in the right orbit, with no other signs of systemic involvement. Cerebrospinal fluid analysis demonstrated lymphoma cell infiltration. She was diagnosed with stage IV ENKTL and treated with orbital radiotherapy and systemic chemotherapy, with subsequent remission. However, the lymphoma relapsed in her left vitreous at 10 months after therapy, suggesting metastasis of lymphoma cells to the contralateral eye via the vitreous and cerebrospinal fluid.Conclusions and importanceA few cases of ocular-tissue ENKTL have been reported, mostly involving invasion or dissemination of primary nasal lesions; in contrast, primary orbital and intraocular ENKTL has rarely been reported. To the best of our knowledge, this is the first report of a primary orbital ENKTL metastasizing to the vitreous of the contralateral eye. Although ENKTL is rare in the orbit and intraocular tissues, it should be considered as a possible differential diagnosis in patients with orbital tumors or intraocular inflammation resistant to steroid therapy because ENKTL has a very poor prognosis in the advanced stage.

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