Born in 1958, Prof Johnston is a past pupil of St Columb's College in Derry.
Married with four grown-up sons, he is a globally-recognised cancer specialist. Since 2007 he has led the development of a new international medical school at Queen's and a world-leading Institute of Health Sciences. He is also former director of the Centre for Cancer research and Cell Biology at Queen's.
In 2012 he accepted a Diamond Jubilee Queen's Anniversary Prize awarded by the Queen for the university's leadership of the Comprehensive Cancer Centre and its achievement in reducing cancer mortality rates in the north over the past decade.
He is the third St Columb's old boy to assume a high-profile public role in recent years following the appointment of Sir Declan Morgan as lord chief justice and Eamon Martin as coadjutor archbishop of Armagh and future head of the Catholic Church in Ireland.