Investor nerves flared across crypto equities as the latest U.S. proposal on stablecoin rules put circle stock and its reward model in the spotlight. Circle shares, trading under ticker CRCL, plunged as much as 18% on Tuesday after a new draft of the U.S. Clarity Act raised the prospect of sweeping limits on stablecoin yield. Moreover, Coinbase (COIN), which shares revenue from USDC, dropped about 8% in the same early U.S. session.