PLAGL2 and POFUT1 are regulated by an evolutionarily conserved bidirectional promoter and are collaboratively involved in colorectal cancer by maintaining stemness

Daojiang Li; Changwei Lin; Nanpeng Li; Yuheng Du; Chunxing Yang; Yang Bai; Zhicai Feng; Chen Su; Runliu Wu; Shenglei Song; Peicheng Yan; Miao Chen; Arad Jain; Lihua Huang; Yi Zhang; Xiaorong Li

doi:10.1016/j.ebiom.2019.06.051

PLAGL2 and POFUT1 are regulated by an evolutionarily conserved bidirectional promoter and are collaboratively involved in colorectal cancer by maintaining stemness

EBioMedicine. 2019 Jul:45:124-138. doi: 10.1016/j.ebiom.2019.06.051. Epub 2019 Jul 4.

Authors

Daojiang Li¹, Changwei Lin², Nanpeng Li², Yuheng Du², Chunxing Yang², Yang Bai², Zhicai Feng³, Chen Su², Runliu Wu², Shenglei Song², Peicheng Yan², Miao Chen², Arad Jain⁴, Lihua Huang⁵, Yi Zhang², Xiaorong Li⁶

Affiliations

¹ Department of gastroenterological surgery, The Third XiangYa Hospital of Central South University, Changsha, Hunan 410013, China; Department of Colorectal and Anal Surgery of Zhongnan Hospital of Wuhan University, Wuhan 430071, Hubei Province, China.
² Department of gastroenterological surgery, The Third XiangYa Hospital of Central South University, Changsha, Hunan 410013, China.
³ Department of Burns and Plastic Surgery, the 3rd Xiangya Hospital, Central South University, Changsha, Hunan 410013, China.
⁴ College of Arts and Science, University of Virginia, Charlottesville, Virginia 22904, United States of America.
⁵ Center for Experimental Medicine, The Third XiangYa Hospital of Central South University, Changsha, Hunan 410013, China.
⁶ Department of gastroenterological surgery, The Third XiangYa Hospital of Central South University, Changsha, Hunan 410013, China; Center for Experimental Medicine, The Third XiangYa Hospital of Central South University, Changsha, Hunan 410013, China. Electronic address: xiaorongli@csu.edu.cn.

Abstract

Background: Our previous study revealed that PLAGL2 or POFUT1 can promote tumorigenesis and maintain significant positive correlations in colorectal cancer (CRC). However, the mechanism leading to the co-expression and the underlying functional and biological implications remain unclear.

Methods: Clinical tumor tissues and TCGA dataset were utilized to analyze the co-expression of PLAGL2 and POFUT1. Luciferase reporter assays, specially made bidirectional promoter vectors and ectopic expression of 3'UTR were employed to study the mechanisms of co-expression. In vitro and in vivo assays were performed to further confirm the oncogenic function of both. The sphere formation assay, immunofluorescence, Western blot and qRT-PCR were performed to investigate the effect of both genes in colorectal cancer stem cells (CSCs).

Findings: PLAGL2 and POFUT1 maintained co-expression in CRC (r = 0.91, p < .0001). An evolutionarily conserved bidirectional promoter, rather than post-transcriptional regulation by competing endogenous RNAs, caused the co-expression of PLAGL2 and POFUT1 in CRC. The bidirectional gene pair PLAGL2/POFUT1 was subverted in CRC and acted synergistically to promote colorectal tumorigenesis by maintaining stemness of colorectal cancer stem cells through the Wnt and Notch pathways. Finally, PLAGL2 and POFUT1 share transcription factor binding sites, and introducing mutations into promoter regions with shared transcription regulatory elements led to a decrease in the PLAGL2/POFUT1 promoter activity in both directions.

Interpretation: Our team identified for the first time a bidirectional promoter pair oncogene, PLAGL2-POFUT1, in CRC. The two genes synergistically promote the progression of CRC and affect the characteristics of CSCs, which can offer promising intervention targets for clinicians and researchers. FUND: National Nature Science Foundation of China, the Hunan province projects of Postgraduate Independent Exploration and Innovation of Central South University.

Keywords: Bidirectional promoter; Cancer stem cell; Co-expression; Colorectal cancer; PLAGL2; POFUT1.

MeSH terms

3' Untranslated Regions / genetics
Animals
Carcinogenesis / genetics
Cell Line, Tumor
Cell Proliferation / genetics
Colorectal Neoplasms / genetics*
Colorectal Neoplasms / pathology
DNA-Binding Proteins / genetics*
Fucosyltransferases / genetics*
Gene Expression Regulation, Neoplastic / genetics
Humans
Mice
Neoplastic Stem Cells / metabolism
Promoter Regions, Genetic / genetics*
RNA-Binding Proteins / genetics*
Transcription Factors / genetics*
Xenograft Model Antitumor Assays

Substances

3' Untranslated Regions
DNA-Binding Proteins
PLAGL2 protein, human
RNA-Binding Proteins
Transcription Factors
Fucosyltransferases
polypeptide fucosyltransferase