"JPMorgan Chase dominates stock market moves in midday and premarket trading"

JPMorgan Chase acquired First Republic Bank and most of its assets, causing First Republic shares to be halted and JPMorgan shares to rise 3%. Morgan Stanley upgraded General Motors to overweight, causing the automaker's shares to gain 2%. Norwegian Cruise Line jumped 8% after reporting better-than-expected quarterly results and boosting its full-year profit forecast. Exxon Mobil shares shed 3% after a Goldman Sachs downgrade to neutral. On Semiconductor jumped 7% after beating first-quarter earnings and revenue expectations.