The Sensex at the Bombay Stock Exchange gained 152 points, or 1 per cent, to 15,966 in early trade, this morning, on buying by funds and retail investors, tracking firm Asian markets.Later, the Sensex picked up steam, and stood a solid 279 points or 1.8 percent in positive territory, to cross the 16,000 mark, at 16,093, in afternoon trade.Other key stock indices in Japan, China, Hong Kong, Singapore, South Korea and Taiwan had gained between 0.8 percent and 2.6 percent, today, on optimism that the US economy is weathering Europe's sovereign-debt crisis. Over in the US, the Dow Jones Industrial Average had climbed 0.3 per cent, overnight.