US STOCKS-Wall Street to open higher, Yellen remarks awaited
* Yellen speech eyed for clues on interest rates
* Prana Biotech tumbles after Alzheimer's drug study results
* Chicago PMI on tap
* Futures up: Dow 81 pts, S&P 9.25 pts, Nasdaq 21.75 pts (Updates prices)
By Chuck Mikolajczak
NEW YORK, March 31 (Reuters) - U.S. stocks were poised to open higher on Monday, putting the S&P 500 on track for a second straight advance, ahead of a speech by Federal Reserve Chair Janet Yellen.
* Investors will peruse comments by Yellen, who is scheduled to speak in Chicago at 9:55 a.m. EST (1355 GMT), for clues on her stance on interest rates. On March 19, equities dropped after Yellen raised the possibility of an earlier-than-anticipated increase in rates.
* The S&P 500 is nearly flat for the month and up 0.5 percent for the quarter, on pace for the benchmark index's worst quarterly performance since the last quarter of 2012.
* Equities may get a boost on Monday from end of quarter "window dressing," when money managers adjust their positions to improve the look of their portfolios. Continuación...