The BSE benchmark 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 30-share Sensex, which closed 158 points higher in the previous session, fell by 151 points, or 0.95 per cent, to 15,707.In a similar fashion, the wide-based National Stock Exchange Nifty Index shed 46.75 points, or 0.98 per cent, to 4,709.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'.