Sison will continue with her other programs at GMA Integrated News and Public Affairs, namely 'Balitanghali,' 'Pinoy MD' and 'One on One: Walang Personalan.'
His addition comes as One News revamps its morning lineup.
Chavez will go head-to-head with fellow entertainment journalists from the UK, Australia and Northern Ireland.
Beginning January 9, De Castro will resume his anchor duties, joining Karen Davilla, Bernadette Sembrano and Henry Omaga Diaz.
The longtime Kapamilya newser will officially take over in January.