Japan’s benchmark equity index Nikkei dropped 1% to trade around 16,000 levels despite moderate gains in the US stock markets.At the time of writing, shares in Tokyo Gas were down 5.15% and were the top loser in Nikkei index. Meanwhile, shares in Japan Steel works and Suzuki Motor Corp were up 2.8% and 2.3% respectively.Japanese stocks had ended higher yesterday, helped in part by uptick in the USD/JPY pair. However, the currency pair failed to take out 105.00 levels and is once again losing height in Asian session today. Consequently, Nikkei is feeling the heat. The losses are also due to caution ahead of Brexit referendum.Nikkei Technical LevelsThe index currently trades at 16,020 levels. The immediate support is seen at 16,000, under which support at 15,837 (5-DMA) and 15,762 (June 13 low) could be put to test. On the other side, breach of resistance at 16,123 (daily high) would open doors for 16,202 (previous day’s high) and 16,322.40 (May 6 low).