* M&A deal lifts sentiment; UnitedHealth unit to buy Catamaran
* Weakness in oil and strength in dollar could be a concern
* Futures up: Dow 88 pts, S&P 9.25 pts, Nasdaq 28.25 pts
By Ryan Vlastelica
NEW YORK, March 30 (Reuters) - U.S. stock index futures rose on Monday, pointing to a second straight daily gain as a trio of M&A deals lifted sentiment after a recent bout of weakness.
* Despite that, energy shares could come under pressure as crude oil fell sharply, due to a possible deal with Iran that could bring an end to sanctions and allow an increase in the country's oil exports. Crude oil fell 1.8 percent to $47.94 per barrel.
* Separately, an increase in the U.S. dollar could weigh on multi-nationals.
* 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 2.7 percent to $121.60 before the bell while U.S. shares of Catamaran added 26 percent to $60.75.
* Ireland's Horizon Pharma Plc said it would acquire Hyperion Therapeutics Inc in an all-cash deal worth about $1.1 billion, while Fujifilm Holdings Corp agreed to acquire U.S. biotechnology firm Cellular Dynamics International Inc for $307 million.
* Hyperion rose 5.6 percent to $45.13 in light premarket trading while 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.
* Trading could be quiet this week as investors look ahead to earnings season, which will start in earnest in mid-April, as well as to the March payroll report, which will be released on Friday, when stock markets are closed for the Good Friday holiday, leaving investors unable to trade on the data until the following week.
* The jobs report will be closely studied for any indication of when the Federal Reserve will raise interest rates for the first time in almost a decade.
Futures snapshot at 6:56:
* S&P 500 e-minis were up 9.25 points, or 0.45 percent, with 111,796 contracts changing hands.
* Nasdaq 100 e-minis were up 28.25 points, or 0.65 percent, in volume of 21,774 contracts.
* Dow e-minis were up 88 points, or 0.5 percent, with 26,557 contracts changing hands.
Editing by Chizu Nomiyama