* WSJ: Mueller's team subpoenaed Trump's campaign in Oct
* Dollar slips after gaining overnight on improving risk appetite (Updates throughout)
TOKYO, Nov 17 (Reuters) - The dollar slipped on Friday, weakened by a Wall Street Journal report that investigators into possible Russian interference in the 2016 U.S. presidential election had subpoenaed President Donald Trump's election campaign for documents.
Special Counsel Robert Mueller's team issued the subpoena last month for documents containing specified Russian keywords from more than a dozen officials, according to the report.
The dollar index against a basket of six major currencies was down 0.35 percent at 93.593.
The index had edged up overnight to pull away from a four-week trough of 93.402 set on Wednesday. Wall Street shares rallied overnight after sagging through much of the week, causing a 4 basis points jump in the long-term Treasury yield to shore up the dollar.
"Dollar selling picked up after the market became aware of the Wall Street Journal's report," said Yukio Ishizuki, senior currency strategist at Daiwa Securities in Tokyo.
"Dollar demand from institutional investors appeared quite strong but selling by speculators seemed even stronger. We are likely to see choppy moves as participants try to adjust their positions before Thanksgiving Day (on Nov. 23)."
The greenback dropped about 0.6 percent to 112.405 yen , lowest since Oct. 19.
The dollar had bounced overnight from a one-month low of 112.470 yen midweek as an ebb in investor confidence halted a surge in global equities and lifted the Japanese currency.
"While the comeback in equities has stopped the recent decline in Treasury yields, focus remains on U.S. tax reforms," said Junichi Ishikawa, senior forex strategist at IG Securities in Tokyo.
"Yields cannot rise much further when it is unclear whether tax reforms can go through this year. Dollar/yen can test the 114.00 handle but lacks momentum for a sustained surge under such conditions."
The U.S. House of Representatives on Thursday approved a broad package of tax cuts sought by Trump. The debate now moves to the Senate, where Republican majority is smaller and no decisive action is expected until after next week's Thanksgiving holiday.
The euro rose 0.35 percent to $1.1814, paring overnight losses.
The common currency was on track to gain 1.2 percent on the week. It had rallied to a one-month high of $1.1862 on Wednesday after data showed strong growth for Germany's economy in the third quarter.
Against the sagging dollar, sterling extended gains after drawing support overnight when an initiative by European Central Bank President Donald Tusk on Brexit negotiations was taken as mildly positive.
The pound rose 0.35 percent to $1.3238 to put further distance between the week's low of $1.3063 marked on Monday when perceived troubles for British Prime Minister Theresa May hurt the currency.
The Australian dollar crawled up 0.15 percent to $0.7598 . It was still poised to end 1 percent lower on the week, during which it sank to a near five-month low of $0.7567 on lower commodity prices and weak domestic data. (Reporting by Shinichi Saoshiro; Editing by Simon Cameron-Moore)