The CBI is examining the role Dayalu Ammal, wife of DMK chief M Karunanidhi, played in the affairs of Kalaignar TV to file a chargesheet against her in the 2G scam. The  agency has to file its supplementary chargesheet by April 25. CBI has alleged Kalaignar TV received up to Rs200 crore from Shahid Usman Balwa’s company DB Realty via two intermediary companies — Kusegaon Fruits & Vegetables (now Kusegaon Realty) and Cineyug.