Interferon regulatory factor-2 regulates cell growth through its acetylation

Area of Science:

• Molecular Biology
• Cellular Biology
• Epigenetics

Background:

• Interferon regulatory factor-2 (IRF-2) is known to be acetylated by p300 and PCAF.
• Acetylation is a key post-translational modification regulating protein function.

Purpose of the Study:

• To identify the specific acetylation sites on IRF-2.
• To investigate the functional consequences of IRF-2 acetylation on DNA binding and transcriptional activity.
• To determine the role of IRF-2 acetylation in cell growth regulation.

Main Methods:

• Mass spectrometry to identify acetylation sites.
• Site-directed mutagenesis to create acetylation-deficient IRF-2 mutants.
• Reporter gene assays to measure promoter activity.
• Chromatin immunoprecipitation (ChIP) assays to assess promoter binding in vivo.

Main Results:

• Lys-75 and Lys-78 in the DNA binding domain (DBD) were identified as major IRF-2 acetylation sites.
• Acetylation of IRF-2 did not affect in vitro DNA binding, but mutation of Lys-75 impaired IRF-2-dependent histone H4 promoter activation.
• IRF-2 acetylation and H4 promoter activity were observed only in growing cells, not in growth-arrested cells.
• Mutation of Lys-78 abolished DNA binding activity, independent of acetylation.
• IRF-2 interacted with p300 and bound to the H4 promoter in growing cells, as shown by ChIP.

Conclusions:

• IRF-2 acetylation occurs in a cell growth-dependent manner.
• Lys-75 acetylation is essential for IRF-2's role in transcribing cell growth-regulated promoters, like histone H4.
• These findings highlight the importance of IRF-2 post-translational modification in linking cell growth and transcriptional regulation.