The former Ulster Unionist leader, David Trimble, is to resign from the party and join the Conservatives.
Mr Trimble, who was First Minister in Northern Ireland's first power-sharing administration, is a member of the House of Lords.
He did not contest the Assembly elections in March.
The DUP leader, Ian Paisley, earlier said he was heartened by the response everywhere he goes to the recent political developments in Northern Ireland.
This morning Mr Paisley confirmed that the DUP's ministers in the Northern Ireland Assembly will be Peter Robinson, Nigel Dodds, Arlene Foster and Edwin Poots.
Dr Paisley's son, Ian Paisley Junior, has been given the role of Junior Minister in the office of First and Deputy First Minister.
Mr Robinson will take the Finance and Personnel portfolio, Mr Dodds will be Minister for Enterprise, Trade & Investment, Ms Foster will take charge at the Dept of the Environment and Mr Poots will be the Minister for Culture, Arts & Leisure.
Five of the DUP's Westminster MPs will be appointed to chair assembly committees.
Sammy Wilson will be the Education chairperson; Iris Robinson will be the Health Committee chairperson; Willie McCrea will chair the Agriculture Committee; Gregory Campbell will take the Social Development Committee chair and Jeffrey Donaldson has been placed in the new Institutional Review Committee.
Mr Donaldson will also lead the four-person DUP team on the Northern Ireland Policing Board.
The party's other representatives will be Peter Weir, David Simpson and Tom Buchanan.
Mr Paisley said that he is heartened by the response, everywhere he goes, to the recent political developments in Northern Ireland.
SF in policing board talks
Separately, Sinn Féin is holding its first formal meeting with the Policing Board this morning.
Sinn Féin President Gerry Adams is meeting the chairman of the board in Belfast to discuss police collusion with loyalist paramilitaries.
A party delegation at Stormont will consider police accountability and increasing the number of republicans in the force.
It follows Sinn Féin's commitment to undertake police oversight duties once power is devolved.
On 8 May, the party is to take up positions in an executive alongside Mr Paisley's Democratic Unionist Party.
Elsewhere, the director of a victims' group in Northern Ireland has said he is taking seriously reports of a threat by loyalist paramilitaries against him.
Mark Thompson of Relatives for Justice blamed the Ulster Volunteer Force after being warned of the risk by police in west Belfast on Saturday.
