Isolation of a DNA fragment that is expressed as an amber suppressor when present in high copy number in yeast.

A plasmid carrying a DNA sequence conferring amber suppression has been isolated from yeast pool 35 DNA. The plasmid YEp13-SUP suppresses the amber mutations rad50-1 and trp1-289 as well as other known amber mutations. This sequence is located on the 2.5-kb insert and is expressed only when the plasmid bearing it is present in high copy number. The suppressor sequence was shown to integrate close to the MAL4 gene located on the right arm of chromosome XI.