Erasing initial gains, the Sensex at the Bombay Stock Exchange was trading 72 points in the negative territory at 15,383 in afternoon trade.In the opening trade today, the 30-share index rose by 69 points to 15,524 after the government decided to allow Qualified Foreign Investors to directly invest in the Indian equity market.The broad-based National Stock Exchange Nifty was trading 24 points in the red at 4,601.