Functional regulation of an ancestral RAG transposon ProtoRAG by a trans -acting factor YY1 in lancelet

摘要

The discovery of ancestral RAG transposons in early deuterostomia reveals the origin of vertebrate V(D)J recombination. Here, we analyze the functional regulation of a RAG transposon, ProtoRAG, in lancelet. We find that a specific interaction between the cis-acting element within the TIR sequences of ProtoRAG and a trans-acting factor, lancelet YY1-like (bbYY1), is important for the transcriptional regulation of lancelet RAG-like genes (bbRAG1L and bbRAG2L). Mechanistically, bbYY1 suppresses the transposition of ProtoRAG; meanwhile, bbYY1 promotes host DNA rejoins (HDJ) and TIR-TIR joints (TTJ) after TIR-dependent excision by facilitating the binding of bbRAG1L/2?L to TIR-containing DNA, and by interacting with the bbRAG1L/2?L complex. Our data thus suggest that bbYY1 has dual functions in fine-tuning the activity of ProtoRAG and maintaining the genome stability of the host. Lancelet expresses an ancestral RAG transposon, ProtoRAG, which predates human RAGgenes that are responsible for V(D)J recombination and adaptive immunity repertoire generation. Here the authors show that ProtoRAG is functionally regulated by a trans-acting factor, bbYY1, for tuning transposon activity and maintaining genome stability.