Ets1 and heat shock factor 1 regulate transcription of the Transformer 2β gene in human colon cancer cells.
BACKGROUND
Transformer (Tra) 2β is a member of the serine/arginine-rich (SR)-like protein family that regulates alternative splicing of numerous genes in a concentration-dependent manner. Several types of cancer cells up-regulate Tra2β expression, while the regulatory mechanism of Tra2β expression remains to be elucidated. In this study, we examined the transcriptional regulation and possible functions of Tra2β in human colon cancer cells.


METHODS
We cloned 959 bp-upstream of the human TRA2β 5'-flank into luciferase constructs. Chromatin immunoprecipitation (ChIP) was employed to identify crucial cis element(s) and trans activator(s) of the TRA2β promoter. Tra2β expression in the human colon and colon cancer tissues was examined by immunohistochemistry.


RESULTS
In response to sodium arsenite, colon cancer cells (HCT116) increased levels of TRA2β1 mRNA encoding a functional, full-length Tra2β with a peak around 6 h without changing its mRNA stability. Transient expression assays using a reporter gene driven by serially truncated TRA2β promoters and Chip assay demonstrated that an Ets1-binding site present at -64 to -55 bp was crucial for basal transcription, while three heat shock elements (HSEs) located at -145 to -99 bp mediated the oxidant-induced transactivation of TRA2β. Tra2β knockdown caused apoptosis of HCT116 cells. Tra2β were preferentially expressed in proliferative compartment of normal human colonic glands and adenocarcinomas, where Ets1 and heat shock factor 1 were also highly expressed.


CONCLUSIONS
Our results suggest that oxidative stress-responsive Tra2β may play an important role in colon cancer growth.
Department of Stress Science, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan.
Keisuke
K
Kajita
Yuki
Y
Kuwano
Naruka
N
Kitamura
Yuzuru
Y
Satake
Kensei
K
Nishida
Ken
K
Kurokawa
Yoko
Y
Akaike
Manami
M
Honda
Kiyoshi
K
Masuda
Kazuhito
K
Rokutan
D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D018053:Arsenites / Q000494:pharmacology; D001483:Base Sequence; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D000076249:Heat Shock Transcription Factors; D018869:Heat-Shock Response / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D018384:Oxidative Stress / Q000235:genetics; D011401:Promoter Regions, Genetic; D050784:Proto-Oncogene Protein c-ets-1 / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D016601:RNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D017670:Sodium Compounds / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D018053:Arsenites; D004268:DNA-Binding Proteins; C494041:ETS1 protein, human; D000076249:Heat Shock Transcription Factors; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D050784:Proto-Oncogene Protein c-ets-1; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D016601:RNA-Binding Proteins; D017670:Sodium Compounds; C097083:TRA2B protein, human; D014157:Transcription Factors; D000068103:Serine-Arginine Splicing Factors; C017947:sodium arsenite