US STOCKS-Futures climb with Yellen on tap
* Yellen speech eyed for rate clues
* Prana Biotech tumbles after Alzheimer's drug study results
* Chicago PMI on tap
* Futures up: Dow 53 pts, S&P 6 pts, Nasdaq 14.75 pts
By Chuck Mikolajczak
NEW YORK, March 31 (Reuters) - U.S. stock index futures rose on Monday, indicating the S&P 500 will climb for a second straight session, ahead of a speech by Federal Reserve Chair Janet Yellen.
* Yellen is scheduled to speak in Chicago at 9:55 a.m. EST (1355 GMT) and investors will monitor her comments for 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, putting it on pace for its worst quarterly performance since the last quarter of 2012.
* S&P 500 e-mini futures rose 6 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures gained 53 points and Nasdaq 100 futures added 14.75 points. Continuación...