Determine whether JunA- is a Trans-acting Factor or a Cis-acting element?

Complementation test which is also known as cis-trans test can be used to determine whether JunA is a trans acting factor or a cis acting element.Through complementation test, different elements are added to the mutant and its effects on regulation can be studied.If Jun A is the promoter or the operator gene , then no transcription will occur which means that JunA is a cis acting element because promoter and operator in lac operon are always cis acting.If JunA is encodes a repressor protein and that can cause transcription to occur, that means it is trans acting element as repressor diffuses through the cell and binds to the DNA.