ISTANBUL Turkish prosecutors have called on Istanbul University (İÜ) to join an ongoing investigation into allegations that Istanbul Mayor Ekrem İmamoğlu used a fake diploma . The chief public prosecutor’s office in Istanbul sent a letter to the İÜ, requesting information about İmamoğlu’s 1990 undergraduate transfer from the University College of Northern Cyprus (UCNC). At the time, UCNC was not recognized by Turkish authorities, according to a report by Türkiye 's Higher Education Council (YÖK)