* Auto sales expected throughout session
* Best Buy climbs in premarket after results
* Citigroup to sell OneMain Financial to Springleaf Holdings
* Futures off: Dow 17 pts, S&P 2.75 pts, Nasdaq 3.75 pts
By Chuck Mikolajczak
NEW YORK, March 3 (Reuters) - U.S. stock index futures edged lower on Tuesday, after the Dow and S&P marched to new record highs and the Nasdaq topped the 5,000 mark for the first time in 15 years.
* The Nasdaq notched its first close above the milestone 5,000 mark since March 10, 2000, buoyed by a flurry of merger activity, for only the third close above that level in the history of the index. The Dow and S&P closed at their latest records as economic data pointed to a slowly improving economy.
* Investors will look to monthly auto sales data throughout the session for signs on the health of the U.S. economy and the appetite of consumer spending. Fiat Chrysler Automobiles's CEO said Volkswagen is not the ideal candidate for a merger, adding he was exploring various M&A options.
* Electronics retailer Best Buy climbed 4.8 percent to $40.50 in premarket trade after it reported quarterly results, announced a special dividend and the resumption of its share repurchase plan.
* Citigroup gained 1 percent to $54 before the opening bell after it agreed to sell its consumer finance unit OneMain Financial Holdings Inc to subprime lender Springleaf Holdings Inc for $4.25 billion in cash.
* MannKind Corp tumbled 7.5 percent to $6.14 in premarket after Goldman Sachs cut its rating on the stock to "sell" from "neutral" and slashed its price target to $3 from $6 per share.
* European stock markets pulled back from earlier gains spurred by better-than-expected German retail sales data and merger speculation in the Portuguese banking sector, but remained near multi-year highs set in the prior session.
* Japan's Nikkei stock average erased early gains and ended 0.1 percent lower to snap a three-day winning streak, after the yen rebounded from a three-week low against the greenback touched earlier in the session. China stocks tumbled as investor excitement over a weekend interest rate cut waned.
Futures snapshot at 7:28 a.m. EST (1228 GMT):
* S&P 500 e-minis were down 2.75 points, or 0.13 percent, with 71,440 contracts changing hands.
* Nasdaq 100 e-minis were down 3.75 points, or 0.08 percent, in volume of 8,213 contracts.
* Dow e-minis were down 17 points, or 0.09 percent, with 9,905 contracts changing hands. (Reporting by Chuck Mikolajczak; Editing by Chizu Nomiyama)