David John Markey, legal assistant to the chairman of the Federal Communications Commission, has been nominated to be assistant secretary of Commerce for communications and information. Markey previously served as chief of staff for Sen. Frank H. Murkowski (R-Alaska).

The president also has nominated Helen M. Witt, a private arbitrator from Pittsburgh, to be a member of the National Mediation Board.

At the Office of Management and Budget, deputy general counsel Michael McConnell has left to join the Justice Department. And in the OMB's Office of Information and Regulatory Affairs, Dorothy Tella, a former statistical analyst at the CIA and the Social Security Administration, has been tapped to run the statistical policy office.

At the National Security Council, Jack Matlock Jr., currently ambassador to Czechoslovakia, will serve as senior director of European and Soviet affairs and as a special assistant to the president.

In other appointments, John R. Longenecker, director of the Energy Department's Office of Breeder Reactor Projects, has been named deputy assistant secretary for uranium enrichment and assessment.

And Dr. John A. Gronvall has been named deputy chief medical director of the Veterans Administration's Department of Medicine and Surgery. Gronvall, formerly dean of the University of Michigan's medical school, joined the VA in February as deputy assistant chief medical director for academic affairs.