POU5F1/OCT4 Attenuates Human LINE-1 Expression Levels in Induced Pluripotent Stem Cells.

Area of Science:

• Genomics
• Epigenetics
• Stem Cell Biology

Background:

• Long Interspersed Nuclear Element-1 (LINE-1, L1) retrotransposons are highly transcriptionally active in human pluripotent stem cells (PSCs).
• Understanding the regulation of L1 elements in PSCs is crucial for genome stability and cellular function.

Purpose of the Study:

• To investigate the interaction between pluripotency-associated transcription factors (TFs) and L1 elements in human PSCs.
• To elucidate the regulatory role of these TFs in modulating L1 transcriptional activity.

Main Methods:

• Chromatin immunoprecipitation sequencing (ChIP-seq) to identify TF binding sites on L1 elements.
• Analysis of chromatin accessibility (ATAC-seq) and histone modifications (H3K4me3).
• Gene knockdown experiments to assess the functional impact of TF binding on L1 expression.

Main Results:

• Pluripotency TFs including POU5F1 (OCT4), SOX2, KLF4, NANOG, and MYC bind to the 5' untranslated region (UTR) of young L1 subfamilies.
• TF binding sites exhibit open chromatin features and H3K4me3 enrichment, indicating potential transcriptional activation.
• Knockdown of POU5F1, SOX2, and NANOG affected L1 expression, with POU5F1 showing a repressive role.

Conclusions:

• Pluripotency TFs bind to transcriptionally competent L1 loci in human PSCs.
• These TFs modulate L1 expression, with varying regulatory roles among different factors.
• TF binding motifs are conserved in older L1 subfamilies, suggesting a role in host fitness and L1 amplification.