The BSE benchmark Sensex today gained over 45 points in early trade on sustained buying by funds and retailers in oil and gas, PSUs, IT and banking sector stocks.The 30-share barometer moved up by 45.67 points, or 0.22 per cent, to trade at 20,072.28 points in early trade. The index had gained 45.04 points yesterday.The wide-based index of National Stock Exchange, Nifty, gained 11.00 points, or 0.18 per cent, to 6,065.30.In the Asian region, Japan's Nikkei rose by 1.28 per cent, while Hong Kong's Hang Seng shed 0.02 per cent in morning trade. The US Dow Jones Industrial Average ended 0.49 per cent higher in yesterday's trade