The yen jumped against the U.S. dollar on Friday, rising by nearly 2 yen at one point to the lower 157 level, on growing speculation about possible intervention by Japanese authorities after the Bank of Japan's decision left the yen weak.The yen depreciated to the lower 159 level after the BOJ kept its policy rate unchanged, and Governor Kazuo Ueda said the central bank is ready to step up bond-buying operations in "exceptional cases" to address a recent sharp rise in bond yields."It is unlikely that a yen-buying intervention has taken place," said Yuzo Sakai, chief manager of business plan…READ FULL ARTICLE