Long interspersed nuclear element-1 expression and retrotransposition in prostate cancer cells

Erica M Briggs,Ilaria Sciamanna,Susan Ha,Paolo Mita,Corrado Spadafora,Susan K Logan,Gregory Brittingham

doi:10.1186/s13100-017-0106-z

Abstract

BackgroundLong Interspersed Nuclear Element-1 (LINE-1) is an autonomous retrotransposon that generates new genomic insertions through the retrotransposition of a RNA intermediate. Expression of LINE-1 is tightly repressed in most somatic tissues to prevent DNA damage and ensure genomic integrity. However, the reactivation of LINE-1 has been documented in cancer and the role of LINE-1 protein expression and retrotransposition has become of interest in the development, progression, and adaptation of many epithelial neoplasms, including prostate cancer.ResultsHere, we examined endogenous LINE-1 protein expression and localization in a panel of prostate cancer cells and observed a diverse range of LINE-1 expression patterns between cell lines. Subcellular localization of LINE-1 proteins, ORF1p and ORF2p, revealed distinct expression patterns. ORF1p, a nucleic acid chaperone that binds LINE-1 mRNA, was predominantly expressed in the cytoplasm, with minor localization in the nucleus. ORF2p, containing endonuclease and reverse transcriptase domains, exhibited punctate foci in the nucleus and also displayed co-localization with PCNA and γH2AX. Using a retrotransposition reporter assay, we found variations in LINE-1 retrotransposition between cell lines.ConclusionsOverall, our findings reveal new insight into the expression and retrotransposition of LINE-1 in prostate cancer. The prostate cancer cells we investigated provide a unique model for investigating endogenous LINE-1 activity and provide a functional model for studying LINE-1 mechanisms in prostate cancer.

Highlights

Long Interspersed Nuclear Element-1 (LINE-1) is an autonomous retrotransposon that generates new genomic insertions through the retrotransposition of a RNA intermediate
Prostate cancer cell lines express LINE-1 ORF1 and ORF2 protein To investigate endogenous LINE-1 proteins in prostate cancer we examined their expression in a variety of prostate cancer cells
We utilized antibody against ORF2 protein (ORF2p) [17] to determine whether ORF2 expression varied among the cell lines and whether ORF2p expression correlated with ORF1 protein (ORF1p) levels (Fig. 1a)

Summary

Introduction

Long Interspersed Nuclear Element-1 (LINE-1) is an autonomous retrotransposon that generates new genomic insertions through the retrotransposition of a RNA intermediate. Long Interspersed Nuclear Element-1 (LINE-1) is an autonomous, non-long terminal repeat retrotransposon that constitutes approximately 17% of the human genome [1]. Through the utilization of a RNA intermediate, LINE-1 creates new genomic insertions via a “copy and paste” mechanism known as retrotransposition. ORF1p and ORF2p bind LINE-1 mRNA in the cytoplasm, forming the ribonucleoprotein (RNP). The reverse transcriptase domain of ORF2p utilizes the LINE-1 mRNA as a template and creates a new LINE-1 insertion through Target Primed Reverse Transcription (TPRT) [9]. The retrotransposition cycle is thought to play a role in genomic variation and evolution, and more recently became of interest due to its role in disease initiation and progression [10]

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Results

Discussion

Conclusion