When looking at US markets on Tuesday, one of the biggest losers ended up being Coinbase (NASDAQ:COIN). The cryptocurrency firm lost more than 21% after it was reported that the company isunder investigation by the SECregardingits digital asset listing process. While investors are feeling plenty of pain already, it might not help short term sentiment that one of the firm's biggest backers sold a chunk of its stake during Tuesday's trading.The probe apparently involves whether or not Coinbase improperly let Americans trade digital assets that should have been registered as securities. Last week, Bloomberg reported that a former employee violated insider trading rules by leaking information to help his brother and a friend buy tokens just before they were listed on the platform. Coinbase is