* M&A deal lifts sentiment; UnitedHealth unit to buy Catamaran
* Oil prices volatile amid potential deal with Iran
* Strength in dollar could be a concern
* Futures up: Dow 121 pts, S&P 10.5 pts, Nasdaq 27.75 pts (Updates prices, adds Teva deal and economic data)
By Ryan Vlastelica
NEW YORK, March 30 (Reuters) - U.S. stock index futures indicated a higher open on Monday, pointing to a second straight daily gain as four M&A deals in the biotech sector lifted market sentiment after a recent bout of weakness.
Despite that, energy shares could come under pressure as crude oil fell on a possible deal with Iran, which could bring an end to sanctions and allow an increase in the country's oil exports. Crude oil fell 0.5 percent to $48.68 per barrel after falling as 2.5 percent earlier in the session.
Separately, an increase in the U.S. dollar could weigh on multi-nationals. The U.S. dollar index rose 0.7 percent.
Both the dollar and commodity prices have given investors reason to be cautious of late, especially going into the first-quarter earnings season, where traders will look to see how much oil prices and the strong U.S. dollar will impact corporate bottom lines. Last week, the S&P 500 fell 2.2 percent, the Dow lost 2.3 percent and the Nasdaq declined 2.7 percent.
In deal news, OptumRx Corp, a unit of UnitedHealth Group , agreed to buy pharmacy benefit manager Catamaran Corp in a deal worth $12.78 billion. Shares of UnitedHealth, a Dow component, rose 4.1 percent to $122.80 before the bell while U.S. shares of Catamaran added 26 percent to $60.40.
Among other billion-dollar deals, Ireland's Horizon Pharma Plc said it would acquire Hyperion Therapeutics Inc in an all-cash deal worth about $1.1 billion, while Teva Pharmaceutical said it would buy Auspex Pharmaceuticals Inc for $3.5 billion.
Horizon rose 17 percent to $25.55 on the Nasdaq while Hyperion rose 7.4 percent to $45.89 in premarket trading. U.S. shares of Teva fell 1.3 percent to $61.16 before the bell while Auspex added 42 percent to $100.34.
Separately, Fujifilm Holdings Corp agreed to acquire U.S. biotechnology firm Cellular Dynamics International Inc for $307 million. Cellular more than doubled in premarket and was among the most active Nasdaq stocks.
The deals follow reports last week of Intel Corp being in talks to buy Altera Corp in a deal that could top $10 billion.
In the latest economic data, U.S. consumer spending barely rose in February as households boosted savings to their highest level in more than two years, the latest sign that economic growth slowed sharply in the first quarter.
Futures snapshot at 8:36:
* S&P 500 e-minis were up 10.5 points, or 0.51 percent, with 138,928 contracts changing hands.
* Nasdaq 100 e-minis were up 27.75 points, or 0.64 percent, in volume of 26,381 contracts.
* Dow e-minis were up 121 points, or 0.69 percent, with 31,284 contracts changing hands.
Editing by Chizu Nomiyama