* 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 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.
* At 9:45 a.m. (1345 GMT), Chicago PMI data for March is due. Expectations are for a reading of 59 versus the prior 59.8. Investors will continue to eye data for signs of improvement after lackluster data over the past several weeks was discounted due to harsh winter weather.
* U.S.-listed shares of Prana Biotechnology Ltd tumbled 62 percent to $3.75 before the opening bell after the company said its experimental drug to treat Alzheimer's disease failed to meet the main goal of a mid-stage study in patients with a mild form of the condition.
* Many biotechnology stocks have come under pressure recently, and the Nasdaq Biotechnology index fell 7 percent last week for a fifth week of declines.
* European equities rose for a fifth session to a three-week high on growing speculation that the European Central Bank could ease its policy and China might take steps to stimulate its economy.
* Asian stocks edged higher in a cautious start to the week, with investors holding out hope that China would take steps to stimulate its economy. (Editing by Bernadette Baum)