TOKYO, Nov 9 Japan's Nikkei fell to a four-week closing low on Friday, led by exporter shares, as a looming U.S. fiscal crisis threatened to tip the world's largest economy into recession and as uncertainty over a Greek bailout rekindled worries about the euro zone. The Nikkei ended 0.9 percent lower at 8,757.60, falling for the fifth straight session. It was down 3.2 percent this week, its worst weekly performance in four weeks. The benchmark is still up 3.6 percent this year. The broader Topix lost 0.6 percent to 730.74.