US STOCKS-Futures flat after six straight days of gains

* S&P 500, Nasdaq on six-day winning streak as of Tuesday

* Gilead Sciences (NasdaqGS: GILD - news) rises in premarket after results

* Key earnings on tap; Apple (NasdaqGS: AAPL - news) , Facebook (NasdaqGS: FB - news) out after the close

* Futures down: Dow 5 pts, S&P 2.1 pts, Nasdaq 7 pts

By Ryan Vlastelica

NEW YORK (Frankfurt: HX6.F - news) , April 23 (Reuters) - U.S. stock index futures were flat on Wednesday as investors found few reasons to keep buying following six straight days of gains on both the S&P 500 and Nasdaq.

* Equities have recently been boosted by corporate earnings, with a number of prominent names topping expectations, though companies have largely been beating reduced forecasts. According to Thomson Reuters (Frankfurt: TOC.F - news) data, profits are seen rising 1.1 percent this quarter, down from the 6.5 percent growth rate estimated at the start of the year.

* Gilead Sciences Inc rose 3.8 percent to $75.60 in heavy premarket trading a day after the drugmaker reported a sharp increase in its quarterly profit, helped by sales of its hepatitis C drug. Gilead's results, like those of Netflix Inc (NasdaqGS: NFLX - news) , showed there was still room to grow in high-flying names that recently plunged on signs of excessive valuation.

* Shares of Boeing Co (NYSE: BA - news) rose 2.3 percent to $130.50 after the planemaker reported its first-quarter results and raised its full-year outlook for core earnings.

* Procter & Gamble Co reported third-quarter sales that were slightly under expectations. The Dow component's chief executive said the company was operating "in a slow-growth, highly competitive environment."

* More key reports are expected Wednesday, with Apple Inc and Facebook Inc scheduled for release after the market closes.

* With 20 percent of the S&P 500 having reported results through Tuesday morning (Frankfurt: TDM.F - news) , 63 percent have topped earnings expectations, according to Thomson Reuters data, matching the long-term average. On the revenue side, 51 percent have exceeded forecasts, below the 61 percent long-term average.

* S&P 500 futures fell 2.1 points 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 dipped 5 points and Nasdaq 100 futures lost 7 points.

* Both the S&P 500 and Nasdaq closed out six straight days of gains on Tuesday. The S&P rose 3.5 percent over that period while the Nasdaq added 4 percent.

* In another positive sign for equities, the Dow Jones Transportation Average rose 0.6 percent on Tuesday to close at a record high, its first since April 2. However, trading volume was light, suggesting a lack of investor conviction behind the move.

* AT&T Inc (NYSE: T - news) late Tuesday raised its full-year revenue growth outlook, citing its acquisition of LEAP wireless (Stuttgart: LWI.SG - news) in March and the popularity of a new handset pricing model that charges customers for devices separately from their wireless plans. Shares of the Dow component fell 1.4 percent to $35.78 in premarket trading.

* JetBlue Airways Corp pilots late Tuesday voted by a wide margin to join the Air Line Pilots Association union, raising concerns that the move would raise the airline's costs. Shares fell 0.9 percent to $8.67 in light premarket trading. (Editing by Chizu Nomiyama)