Hematopoietic Cell Stress Response Gene Transcriptional Regulation By TFII‐I and E2F Family

Abstract

TFII‐I is a ubiquitously expressed, multifunctional transcription factor that has been shown to activate and repress transcription. TFII‐I is relatively large and contains a DNA binding domain, a nuclear localization domain, and protein‐protein interaction domains, including 6 R‐repeats that resemble helix‐loop‐helix motifs and a leucine zipper. Genome wide analysis of TFII‐I in human erythroleukemia K562 cells through biotinylation and ChIP sequencing revealed TFII‐I interacting with DNA segments near binding sites for E2F transcription factors. Co‐immunoprecipitation experiments provided data suggesting that E2F1, E2F4, and E2F6 interact with TFII‐I. The E2F family of transcription factors has been shown to regulate G1/S transition stages during the cell cycle. E2F1 works as a transcriptional activator, thereby promoting cell cycle progression, whereas E2F4 and E2F6 are transcriptional repressors and block cell cycle progression. TFII‐I has also been shown to be involved in cell cycle regulation. Chromatin immunoprecipitation (ChIP) experiments revealed binding of TFII‐I and E2F transcription factors at regulatory DNA elements in the Activating Transcription Factor 3 (ATF3)‐gene locus. ATF3 is a transcription factor that binds to the cAMP response element and is a critical component of the cellular stress response. Expression of ATF3 is induced in response to amino acid starvation and/or endoplasmic reticulum stress. Results from the Encode database suggests that transcription factors E2F4 and E2F6 co‐localize with RNA polymerase II at the ATF3 promoter just upstream of a TFII‐I binding site. By treating K562 cells with histidinol and thapsigargin to induce amino acid starvation or endoplasmic reticulum stress, respectively, the upregulation of ATF3 correlated with differential E2F binding patterns in the promoter region. Moreover, TFII‐I knockdown prompted reduced interactions of E2F4 and E2F6 at the ATF3 gene locus. These findings direct us to conclude that the associations between E2F4/6 and TFII‐I may have intricate roles in the configuration of the ATF3 gene locus thereby regulating mechanisms of cellular stress response.Support or Funding InformationMahmoud Aryan, Alex X. Fan, PhD1, Mir Hossain, MS1, and Jörg Bungert, PhD1 1Department of Biochemistry and Molecular Biology, Center for Epigenetics, Powell Gene Therapy Center NIDDK: RO1DK083389, RO1D0K52356