Searching for novel ATF4 target genes in human hepatoma cells by microarray analysis

Area of Science:

• Molecular Biology
• Cellular Stress Response
• Gene Regulation

Background:

• Activating transcription factor 4 (ATF4) is a key transcription factor induced by cellular stresses like endoplasmic reticulum stress.
• ATF4 plays a significant role in regulating cellular processes, including lipid metabolism.
• Understanding ATF4's regulatory targets is crucial for deciphering its role in cellular homeostasis.

Purpose of the Study:

• To identify novel target genes of ATF4, with a specific focus on those involved in lipid metabolism.
• To investigate the regulatory mechanism by which ATF4 controls the expression of these newly identified target genes.

Main Methods:

• Microarray analysis was employed to screen for potential ATF4 target genes.
• Luciferase reporter assays were used to validate ATF4's transcriptional activity on target gene promoters.
• Site-directed mutagenesis was performed to examine the role of the amino acid response element (AARE) in ATF4-mediated gene activation.

Main Results:

• C12orf39, CSTA, and CALCB were identified as novel ATF4 target genes through microarray analysis.
• The promoter regions of C12orf39, CSTA, and CALCB contain an amino acid response element (AARE), a known ATF4-binding site.
• Luciferase assays confirmed that ATF4 significantly activates C12orf39 promoter activity.
• Deletion or mutation of the AARE sequence in the C12orf39 promoter abolished ATF4-mediated activation, confirming its functional importance.

Conclusions:

• C12orf39, CSTA, and CALCB are newly discovered target genes regulated by ATF4.
• ATF4 directly activates the transcription of C12orf39, utilizing the AARE in its promoter region.
• These findings enhance our understanding of ATF4's role in gene regulation and lipid metabolism.