Gcn4 is a transcription factor and a “master regulator” for gene expression which regulates close to one tenth of the yeast genome.In a study by Razaghi et al, amino acid starvation activated the transcription factor Gcn4p, resulting in transcriptional induction of almost all genes involved in amino acid biosynthesis, including HIS4. Thus involvement of Gcn4 in regulation of both histidinol dehydrogenase HIS4 and interferon gamma hIFNγ was hypothesised as a scenario explaining the increased level of hIFNγ under amino acid starvation.