New gene expression modulator

Transposons inhibiting transcription could have had profound effect on evolution

Cathy Holding(cathyholding@aol.com)
May 18, 2004

A novel gene regulatory mechanism with profound implications for the evolutionary biology of mammalian genomes is described in May 20 Nature by a group at the Johns Hopkins School of Medicine, Baltimore, led by Jef D. Boeke.

Open reading frames of Line-1 (L1) elements—the most abundant autonomous retrotransposons in the human genome—have the ability “quash” gene expression when inserted into RNA transcripts, according to Boeke.

Boeke's team fused the L1 sequence encoding the open reading frame endonuclease/reverse transcriptase (ORF2) in the sense orientation downstream of a reporter promoter. This led to “a potent transcriptional elongation block that was shown to be dependent on length and the high A content of the open reading frame,” Boeke told The Scientist.

When the sequence was fused in the antisense orientation, there were some RNA polymerases that made it all the way through, “but about 85% of the time, what we saw...

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