The judges of the several courts, the Attorney General, district attorneys, the Secretary of State, the Auditor, the Treasurer, the Commissioner of Agriculture and Industries, the Commissioner of Conservation and Natural Resources, the Public Service Commissioners, the Director of the Department of Revenue, the Director of the Department of Finance, the Commissioner of Corrections, the Director of Industrial Relations, the Director of the State Department of Human Resources, the Clerk of the Supreme Court, the clerks of the circuit courts, the sheriffs, the tax assessors, the tax collectors, the county treasurers, the county commissioners, the constables and all other officers when specifically required by other provisions of law, before entering upon and exercising the duties of their respective offices, must obtain a commission.