* ADP report shows fewer jobs added in May than expected
* Many investors worry about low volume and volatility
* Protective Life jumps in premarket, Dai-ichi to buy
* Futures down: Dow 19 pts, S&P 3.6 pt, Nasdaq 9 pts (Adds ADP data)
By Ryan Vlastelica
NEW YORK, June 4 (Reuters) - U.S. stock index futures pointed to a lower open on Wednesday as data on the labor market came in weaker than expected, giving investors reason to sell amid few positive catalysts and with indexes near record levels.
* About 179,000 private sector jobs were added in May, well below the 210,000 that had been expected, according to the ADP National Employment Report. April's job gains were revised loser by 5,000.
* The report comes after a string of economic indicators pointed to improving conditions, and it could raise caution for Friday's closely watched non-farm payrolls report.
* Equities have been strong lately, with the S&P 500 up for seven of the past nine sessions, hitting multiple records over that period. However, the gains have come in anemic trading volume, suggesting the rally lacks conviction.
* Another potential trading catalyst will come at 10:00 a.m. (1400 GMT), when the Institute for Supply Management's May read on services will be released. Analysts expect it to rise by 0.3 to 55.5.
* S&P 500 futures fell 3.6 point and were below 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 fell 19 points and Nasdaq 100 futures lost 9 points.
* Roughly 118,000 S&P 500 e-mini contracts traded as of 8:30 a.m., suggesting another light day of trading. On Tuesday, the SPDR S&P 500 ETF, typically one of the most heavily traded securities on a given day, had one of its most thinly traded sessions of 2014.
* Along with volume, volatility has been light, despite a 4.1 percent pop in the CBOE Volatility index over the past two sessions. The "fear index" remains below 12, well below the historical average of 20, which has some investors concerned the market has become complacent.
* Market action is expected to spike on Thursday, when the European Central Bank meets. Many investors expect bold action by the bank to fight low inflation and high unemployment.
* In company news, Protective Life jumped 18 percent to $69.30 in heavy premarket trading after Japan's Dai-ichi Life Insurance Co agreed to buy the company for $5.7 billion.
* Tibco Software Inc was the Nasdaq's most active premarket mover, slumping 13 percent to $18.16 a day after the company gave a second-quarter outlook that was sharply below expectations.
* The Wall Street Journal reported that NRG Energy Inc is close to a deal worth more than $800 million to buy Alta Wind Energy Center, the largest wind farm in North America.
* Fuel cell companies were weak in premarket trading, with FuelCell Energy down 14 percent to $2.04 and Plug Power Inc off 4.1 percent to $4.23. Both names were among the Nasdaq's most active before the bell.
* Financial information service provider Markit Ltd (IPO-MRKT.O) said it expected its initial public offering to be priced at $23-$25 per share, which could value the company at up to $4.47 billion.
(Editing by Bernadette Baum)