The BSE benchmark Sensex was trading 47 points or 0.30 per cent down at 15,811 points a short while ago. The 30-share Sensex fell by 151 points in opening trade today as participants booked gains recorded in the previous session amid a weakening trend on other Asian bourses.The wide-based National Stock Exchange Nifty was also trading 25 points or 0.53 percent down at 4,731.Meanwhile, in the Asia region, Hong Kong's Hang Seng Index was down by 1.22 per cent and Japan's Nikkei shed 0.32 per cent in morning trade today. The US market was closed yesterday for 'Thanksgiving Day'.