Clayton, an independent, is still awaiting confirmation by the full Senate, which is currently away for Easter recess.
Trump has not yet formally nominated anyone else for the remaining SEC spots - one Democrat and one Republican.
Warren, a progressive Democrat, has been critical of the Trump administration's plans to roll back the 2010 Dodd-Frank Wall Street reform law.
She voted against Clayton's nomination, saying his employment as a lawyer at Sullivan & Cromwell representing large banks creates too many conflicts of interest and may prevent him from being a tough regulator.
As her counsel on the banking committee, Ramamurti has played a prominent role in shaping Warren's policy agenda. He helped steer her investigative efforts into the Wells Fargo fake accounts scandal and worked on bipartisan efforts to broker a deal on housing reforms for mortgage lenders Fannie Mae and Freddie Mac.
This article was provided by Reuters.