Activating transcription factor 4 mediates up-regulation of alanine aminotransferase 2 gene expression under metabolic stress
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Updated: May 4, 2026

Measurements of Physiological Stress Responses in C. Elegans
Published on: May 21, 2020
María C Salgado1, Isidoro Metón1, Ida G Anemaet1
1Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Joan XXIII s/n, 08028 Barcelona, Spain.
Abstract:
Alanine aminotransferase (ALT) provides a molecular link between carbohydrate and amino acid metabolism. In humans, two ALT isoforms have been characterized: ALT1, cytosolic, and ALT2, mitochondrial. To gain insight into the transcriptional regulation of the ALT2 gene, we cloned and characterized the human ALT2 promoter. 5'-deletion analysis of ALT2 promoter in transiently transfected HepG2 cells and site-directed mutagenesis allowed us to identify ATF4 as a new factor involved in the transcriptional regulation of ALT2 expression. Quantitative RT-PCR assays showed that the metabolic stressors histidinol and tunicamycin increased ATF4 levels and up-regulated ALT2 in HepG2 and Huh7 cells. Consistently, knock-down of ATF4 decreased ALT2 mRNA levels in HepG2 and Huh-7 cells. Moreover, ATF4 silencing prevented the activating effect of histidinol and tunicamycin on ATF4 and ALT2 expression. Our findings point to ALT2 as an enzyme involved in the metabolic adaptation of the cell to stress.
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