T-Mobile US Inc TMUS.O gained 2.4% as it raised its full-year postpaid subscriber net additions forecast. Megacap technology-related companies including Apple Inc AAPL.O, Microsoft Corp MSFT.O, Amazon.com Inc AMZN.O, Facebook Inc FB.O and Alphabet Inc GOOGL.O rose between 0.3% and 0.9% in premarket trading. U.S. Treasury Secretary Janet Yellen said on Tuesday she sees no inflation problem brewing, downplaying earlier comments that rate hikes may be needed to stop the economy overheating as President Joe Biden's spending plans boost growth.