A YY1-binding site is required for accurate human LINE-1 transcription initiation.

J N Athanikar

doi:10.1093/nar/gkh698

Abstract

The initial step in Long Interspersed Element-1 (LINE-1) retrotransposition requires transcription from an internal promoter located within its 5'-untranslated region (5'-UTR). Previous studies have identified a YY1 (Yin Yang 1)-binding site as an important sequence in LINE-1 transcription. Here, we demonstrate that mutations in the YY1-binding site have only minor effects on transcription activation of the full-length 5'-UTR and LINE-1 mobility in a single round cultured cell retrotransposition assay. Instead, these mutations disrupt proper initiation of transcription from the +1 site of the 5'-UTR. Thus, we propose that the YY1-binding site functions as a component of the LINE-1 core promoter to direct accurate transcription initiation. Indeed, this sequence may explain the evolutionary success of LINE-1 by enabling full-length retrotransposed copies to undergo autonomous retrotransposition in subsequent generations.

Highlights

Long Interspersed Element-1s (LINE-1s or L1s) are abundant non-long terminal repeat retrotransposons in mammalian genomes that mobilize via a RNA intermediate by a process termed retrotransposition [1,2]
To test whether the Yin Yang 1 (YY1)-binding site is important in retrotransposition, we generated a series of wild-type and mutant LINE-1 expression constructs that contain an indicator cassette in their respective 30-UTRs (Figure 1A) [15,34,35]
We have shown that mutations in the YY1binding site have only minor effects on transcription activation of the full-length 50-untranslated region (50-UTR) and LINE-1 mobility in a single round cultured cell retrotransposition assay

Summary

Introduction

Long Interspersed Element-1s (LINE-1s or L1s) are abundant non-long terminal repeat (non-LTR) retrotransposons in mammalian genomes that mobilize via a RNA intermediate by a process termed retrotransposition [1,2]. ORF1 encodes a 40 kDa RNA-binding protein (p40 or ORF1p) [11,12], whereas ORF2 has the potential to encode a 150 kDa protein with demonstrated endonuclease and reverse transcriptase activities [13,14]. Both proteins are required for retrotransposition in cis [15], which probably occurs by target site-primed reverse transcription (TPRT) [13,16,17]. Recent studies indicate that LINE-1 retrotransposition sometimes leads to other target site rearrangements [18,19,20,21]

Methods

Results

Conclusion